2teaspoonsfinely grated lemon zest/peel, from about 2 lemons
Lemon Frosting:
3tablespoons(42g)butter, softened
2cups(228g)powdered sugar
2tablespoonslemon juice, use the lemons you zested for the cupcakes
½teaspoonvanilla extract
Milk, as needed
1teaspoonfinely grated lemon zest/peel
Freshly grated lemon zest for garnish, if desired
Instructions
Preheat the oven to 350 degree F. Line about 15 muffin cups with paper liners and set aside.
In a medium bowl, combine flour, baking powder, baking soda, and salt; set aside.
In a large bowl, beat the butter with an electric mixer on medium speed for 30 seconds. Add the granulated sugar and vanilla; beat until well mixed. Add the egg and egg yolk and mix well. Add the 1/3 of the flour mixture and mix. Add 1/2 of the sour cream and mix again. Add another 1/3 of the flour mixture, stirring until combined. Add the final 1/2 cup of the sour cream and after mixing, add the final 1/3 of the flour. Mix just until combined. Stir in the 2 teaspoons lemon zest. The batter will have a thick consistency.
Spoon about 1/4 cup of the batter into each prepared muffin cup filling between 1/2 and 2/3 full. Bake the cupcakes for 16-18 minutes until a toothpick inserted in the center comes out clean. Cool completely on a wire rack before frosting.
For the frosting, in a medium bowl, beat the butter, powdered sugar and lemon juice together until light and fluffy, about 1-2 minutes with an electric mixer (stand mixer or handheld). Mix in the vanilla and add 1-2 teaspoons of milk to adjust the consistency, if necessary. It should be creamy and spreadable. Stir in the 1 teaspoon lemon zest. Dollop a tablespoon or two of the frosting on each cupcake and spread until smooth. Top with a few sprinkles of fresh lemon zest, if desired.