preheat oven to 350 F

grease and flour two 9 inch round cake pans and line bottoms with parchment

separate eggs for topping and refrigerate whites if needed.

whisk flour baking powder baking soda and salt

beat butter oil and sugar until light and fluffy then beat in eggs one at a time

mix in lemon zest lemon juice and vanilla

alternate adding dry ingredients and milk mixing just until combined

divide batter evenly into pans and bake until a toothpick comes out clean

cool in pans 10 minutes then turn out and cool completely.

whisk sugar cornstarch and salt in a saucepan then whisk in egg yolks and whole egg followed by lemon juice and zest

cook over medium heat whisking constantly until thick and bubbling

remove from heat and whisk in butter until smooth

cover surface directly with plastic wrap and cool to room temperature then chill until spreadable.

beat egg whites with cream of tartar and salt to soft peaks then gradually beat in sugar until glossy stiff peaks form and beat in vanilla

place one cake layer on a serving plate and spread lemon filling leaving a small border

top with second cake layer and spread remaining filling thinly over top

pile meringue on top and swirl to edges

bake at 350 F for 8 to 12 minutes until lightly browned or briefly broil watching constantly

cool 30 minutes then slice and serve.