In small bowl, whisk egg whites, 1/4 cup of milk, and lemon zest. Set aside.

In mixing bowl, beat butter and sugar until creamy, about 2-3 minutes. Add dry ingredients and mix until combined. Slowly add in egg white mixture and remaining milk, beating well.

Prepare cupcake tins with paper liners. Fill each half full and bake at 350°F for 15 minutes. Cool completely.

For the frosting, beat butter for 3-5 minutes until pale. Add powdered sugar, lemon zest, lemon juice, and cream. Beat until fluffy.

Frost cooled cupcakes with lemon buttercream using a piping bag. Serve and enjoy!