Preheat oven to 350℉ and line a cupcake pan with cupcake liners. Lightly spray each one.
Mix together 1 Tbsp of lemon zest and sugar to release the lemon oils. Set aside.
Mix together the other dry ingredients.
In a measuring cup, mix the lemon juice into the milk and set aside.
In your mixer, add the lemon sugar, butter, and oil. Beat until light and fluffy.
Add in egg yolk, vanilla extract, and the remaining juice and pulp of the lemon. Mix until well combined.
Add in half of the flour mixture and half of the milk, alternating and beating well after each addition.
In a separate mixing bowl, beat egg whites and cream of tartar until stiff peaks form. Fold into batter, and fill cupcake liners ⅔ full.
Bake for 16-20 minutes, until a toothpick inserted in the center comes out clean. Cool on wire racks.