Brown Sugar Rum Cupcakes are my kind of dessert when I want something a little richer than plain vanilla. They’re moist and tender, with that cozy brown sugar flavor and a real (not fake) rum warmth.
The cupcakes have a soft crumb thanks to sour cream, and the rum comes through in a way that tastes grown-up but still dessert-friendly. I top them with a rum brown sugar buttercream that’s smooth, fluffy, and the right match for the caramel-y base.
I like these for holidays, dinner parties, and birthdays where a sheet cake feels too casual. They’re also nice when you want a dessert that pairs well with coffee or a little after-dinner drink.
Why You’ll Love This Recipe
Real brown sugar flavor: Brown sugar shows up in the cupcakes and the frosting, so you get that deeper caramel/molasses taste in every bite.
Moist crumb: The sour cream and milk keep the cupcakes tender, so they don’t bake up dry or spongy.
Rum that actually tastes like rum: Using dark rum gives a warm, rich flavor that doesn’t disappear once baked.
Frosting you can pipe or spread: This buttercream is smooth and stable, so it looks pretty whether you swirl it high or keep it simple.
Easy to dress up: A little turbinado sugar or lime zest on top makes them look finished without extra work.
Ingredients You’ll Need
Cupcakes
- All-purpose flour: I use regular flour here; it gives you a soft cupcake that still holds up to the frosting.
- Baking powder: This gives the cupcakes their lift. Make sure it’s fresh so you don’t end up with flat tops.
- Fine salt: Don’t skip it. It keeps the cupcakes and frosting from tasting one-note sweet.
- Unsalted butter: Softened butter creams better and gives you a smoother batter. If your butter is salty, just go a little lighter on the added salt.
- Light brown sugar: I like light brown sugar for a classic caramel flavor that doesn’t overwhelm the rum.
- Eggs: Room-temperature eggs blend in more evenly, which helps the batter stay smooth.
- Vanilla extract: Vanilla rounds out the brown sugar and rum. Use real extract if you can.
- Whole milk: Whole milk gives a richer cupcake, but 2% will work if that’s what you have.
- Dark rum: Dark rum brings deeper molasses notes. Light rum works too if you want a milder finish.
- Sour cream: This is the moisture insurance. It makes the crumb softer and a little more plush.
Rum Brown Sugar Buttercream
- Unsalted butter: Softened is key so the frosting beats up fluffy instead of lumpy.
- Powdered sugar: Sift it if it looks clumpy. It makes the frosting smoother, especially if you’re piping.
- Light brown sugar: Brown sugar in frosting can feel a bit grainy if it’s dry, so make sure yours is soft and packed.
- Heavy cream or whole milk: Cream makes a richer frosting, but milk is totally fine. Add it slowly so you don’t overthin.
- Dark rum: This is where most of the rum flavor comes through. Add a little, taste, then adjust if you want it stronger.
- Vanilla extract: It helps the frosting taste more balanced and less sugary.
- Salt: Just a pinch makes a big difference here, especially with brown sugar.
Optional
- Turbinado sugar: I like this for a little crunch on top, especially if you pipe a tall swirl of frosting.
- Lime zest: A small pinch wakes up the rum and brown sugar. It’s subtle, but it’s nice.
Recipe Instructions
- Preheat the oven: Heat the oven to 350°F and line a 12-cup muffin pan with paper liners.
- Mix the dry ingredients: Whisk the flour, baking powder, and salt together in a medium bowl until evenly combined.
- Cream the butter and sugar: In a large bowl, beat the softened butter and brown sugar until light and fluffy.
- Add the eggs: Beat in the eggs one at a time, mixing after each one until incorporated.
- Add the vanilla: Mix in the vanilla extract until combined.
- Mix the wet ingredients: In a separate bowl, whisk the milk, rum, and sour cream until smooth.
- Add the flour mixture: Add the dry ingredients to the butter mixture in two additions, alternating with the milk mixture, and mix just until you don’t see dry flour.
- Fill the pan: Divide the batter evenly between the liners, filling each about two-thirds full.
- Bake: Bake for about 18 minutes, until a toothpick comes out clean and the tops spring back lightly when touched.
- Cool the cupcakes: Cool for 5 minutes in the pan, then move to a rack and cool completely before frosting.
- Beat the butter: For the buttercream, beat the butter until smooth and creamy.
- Add the brown sugar: Beat in the brown sugar until well blended.
- Add the powdered sugar: Add the powdered sugar gradually, mixing on low at first, then on medium until fluffy.
- Finish the frosting: Beat in the cream (or milk), rum, vanilla, and salt until smooth and pipeable. Add a little more cream if it’s too thick, or a bit more powdered sugar if it’s too soft.
- Frost the cupcakes: Pipe or spread the buttercream onto the fully cooled cupcakes, then garnish with turbinado sugar or lime zest if you want.
Some of my tips!
This is the part that really makes a difference. If you only read one section, make it this one because this is where I share the little trick that helps the recipe turn out so well.
Recipe Tips & Tricks
Keep everything at room temp. Room-temperature eggs, milk, and sour cream blend in smoothly so the batter doesn’t look curdled. It also helps the cupcakes bake up more evenly.
Don’t overmix once the flour goes in. Mix just until the last streaks of flour disappear. Overmixing is what makes cupcakes turn a little tough.
Use dark rum if you want the flavor to show up. Dark rum gives a deeper, almost caramel-like note. Light rum is fine, but it tastes a bit more subtle in the finished cupcakes.
Wait until the cupcakes are fully cool to frost. Even a little warmth will melt the buttercream and make it slide. If you’re in a hurry, pop the cupcakes in the fridge for a short chill.
Adjust the buttercream with small amounts. Add cream a teaspoon at a time if it’s too thick, and add powdered sugar a tablespoon at a time if it’s too loose. It changes quickly.
Make some touches!
There are plenty of easy ways to serve this depending on the occasion. Keep it simple, or add a few small touches to make it feel a little more special.
Serving Suggestions
- Coffee or espresso: These are really good with coffee, especially something not too sweet. I like them with a latte or plain iced coffee.
- Fresh fruit: A side of berries is nice if you want something bright on the plate. Strawberries and raspberries both work well here.
- Whipped cream: If you’re serving these at a party, a small dollop of lightly sweetened whipped cream looks pretty next to a cupcake. A little lime zest on top ties in nicely.
- After-dinner drinks: A small pour of dark rum, bourbon, or even coffee liqueur works well alongside these. Keep it simple.
Save it for later
This section covers how to store leftovers and what parts of the recipe you can prepare ahead of time.
Storage and Make Ahead
Store frosted cupcakes covered in the fridge for up to 4 days. I let them sit at room temperature for 20 to 30 minutes before serving so the buttercream softens a bit.
If you want to make these ahead, bake the cupcakes the day before and keep them covered. Frost them the next day for the cleanest look and the freshest texture.
You can also freeze unfrosted cupcakes in an airtight container. Thaw at room temperature, then frost once they’re completely thawed and cool.
If the buttercream thickens after chilling, let it sit out briefly and give it a quick stir. It smooths back out pretty easily.
A few quick answers
This section covers a few extra details that may help before you head to the recipe card.
Recipe FAQs
Can I make these alcohol-free?
Yes. Replace the rum with 2 tablespoons milk plus 1 teaspoon rum extract. You’ll still get that rum flavor without the alcohol.
Should I use dark rum or light rum?
I usually use dark rum because it has a deeper, slightly molasses-like flavor that works really well with brown sugar. Light rum is fine if you want a milder finish.
Why did my cupcakes come out dense?
Most of the time it’s from overmixing after the flour is added, or from baking powder that’s past its prime. Mix just until combined, and make sure your baking powder is fresh.
My buttercream seems too soft to pipe. What do I do?
Add a bit more powdered sugar until it holds its shape, or chill the frosting for 10 to 15 minutes and beat it again. If your kitchen is warm, the butter can soften quickly.
You might also like
Before you go, take a look at a few other recipes below the recipe card. They use similar ingredients in a different way and are worth saving too.
MORE DINNER RECIPES TO TRY
Brown Sugar Rum Cupcakes
INGREDIENTS
Cupcakes
- 1.5 cups all purpose flour
- 1.5 tsp baking powder
- ½ tsp fine salt
- ½ cup unsalted butter softened
- ¾ cup packed light brown sugar
- 2 large eggs room temperature
- 2 tsp vanilla extract
- ½ cup whole milk room temperature
- ¼ cup dark rum
- ¼ cup sour cream room temperature.
Rum Brown Sugar Buttercream
- 1 cup unsalted butter softened
- 3 cups powdered sugar sifted
- ⅓ cup packed light brown sugar
- 2 tbsp heavy cream or whole milk
- 2 tbsp dark rum
- 1 tsp vanilla extract
- pinch of salt.
Optional
- turbinado sugar for garnish
- lime zest for garnish.
INSTRUCTIONS
Cupcakes
- Heat oven to 350 F and line a 12 cup muffin pan with liners
- whisk flour baking powder and salt until evenly combined
- cream butter and brown sugar until light and fluffy then beat in eggs one at a time and mix in vanilla
- whisk milk rum and sour cream until smooth then add dry ingredients to the bowl in two additions alternating with the milk mixture mixing just until combined
- divide batter evenly between liners filling each about two thirds full and bake until a toothpick comes out clean and tops spring back then cool 5 minutes in pan and cool completely on a rack before frosting.
Rum Brown Sugar Buttercream
- Beat butter until smooth then beat in brown sugar until well blended
- add powdered sugar gradually and mix on low then medium until fluffy
- beat in cream rum vanilla and salt until smooth and pipeable adding a little more cream if too thick or more powdered sugar if too soft
- pipe or spread onto fully cooled cupcakes and garnish if desired.
