1. For a buttermilk substitute use 1 tbsp lemon juice or vinegar plus enough milk to make 1 cup and rest 5 minutes 2. frosting sets best when poured on a hot cake 3. do not overbake to keep the crumb soft 4. use Dutch process cocoa for deeper color or natural cocoa for a lighter classic flavor 5. store covered at room temperature 2 days or refrigerate up to 5 days and bring to room temperature before serving