2½ cups flour
2 tsp baking powder
½ tsp baking soda
¼ tsp salt
8 oz (2 sticks) / 230 g unsalted butter, slightly softened
1½ cups sugar
2 eggs, room temp.
3 egg yolks, room temp.
2 tsp vanilla extract
2 tsp lemon zest
¼ cup freshly squeezed lemon juice
½ cup milk
Sift together flour, baking powder, baking soda and salt, and set aside.
Beat the butter on medium speed until creamy, gradually add the sugar, increasing the speed slightly until the mixture is light and fluffy. Add the whole eggs and the egg yolks one at a time. Beat in the vanilla and lemon zest. Gradually beat in the lemon juice on low speed (the batter will appear curdled at this point, but will smooth out after you all the dry ingredients). Beat in the the dry ingredients alternating with the milk and mix well. Fill the muffin cups almost to the top and bake in 350°F (180°C) for 18-20 minutes.
3 ounces unsalted butter, softened
1 1/2 cups sifted confectioners’ sugar
1 tsp vanilla extract