Heat oven to 350°F.
Line the bottom of a 9 inch square pan with parchment.
Spray with baking spray. Set aside.
With an electric mixer, beat sugars and butter until well blended, about 1-2 minutes.
Add eggs, one at a time, beating well after each addition.
Continue beating until light and fluffy, 2-3 minutes.
Combine flour, baking powder, and baking soda.
Add to butter mixture alternately with buttermilk, beginning and ending with flour mixture.
Stir in vanilla, lemon juice, and lemon zest.