Prepare Cake Pans: Grease and flour your cake pans (use 3 6-inch round pans or 2 8-inch pans).
Mix Dry Ingredients: Sift together flour, corn starch, baking soda, baking powder, and salt. Set aside.
Cream Mixture: In an electric mixer, beat together vegetable oil, shortening, sugar, vanilla extract, and lemon extract until fluffy.
Add Eggs: Beat in the eggs one at a time, ensuring each is incorporated.
Fold in Lemon Zest: Gently fold in the grated lemon zest.
Combine Ingredients: Alternately fold in the dry ingredients and buttermilk until just combined.
Pour & Bake: Divide the batter into prepared pans. Bake at 325°F for 30-35 minutes or until a toothpick comes out clean.
Cool Down: Cover with plastic wrap and cool in pans for 10 minutes before removing.