Preheat oven to 350 degrees F. Prepare cupcake tins by using liners or spray with non-stick cooking spray
Sift together the flour, baking powder, and salt.
2 1/4 cups cake flour, 1 tablespoon baking powder, 1/2 teaspoon salt
Whisk together the milk and egg whites in a medium bowl.
1 1/4 cups buttermilk, 4 large egg whites
Put the sugar and lemon zest in a mixer bowl or another large bowl and rub them together with your fingers until the sugar is moist and fragrant. Add the butter and, working with the paddle or whisk attachment, or with a hand mixer, beat at medium speed for a full 3 minutes, until the butter and sugar are very light.
1 1/2 cups sugar, lemon zest of two lemons, 1/2 cup unsalted butter
Beat in the extracts and lemon juice, then add one-third of the flour mixture, still beating on medium speed. Beat in half of the milk-egg mixture, then beat in half of the remaining dry ingredients until incorporated.
1 teaspoon pure vanilla extract, 1/4 teaspoon pure lemon extract, 1/4 cup fresh squeezed lemon juice
Add the rest of the milk and eggs, beating until the batter is homogeneous, then add the last of the dry ingredients.
Give the batter a good 2-minute beating to ensure that it is thoroughly mixed and well aerated. Place the batter into the cupcake tins.
Bake for 18-22 minutes, or until the cupcakes are well risen and springy to the touch – a thin knife inserted into the centers should come out clean. Cool on wire rack.