Preheat oven to 350°F and spray a 9X13 inch pan with a non-stick baking spray. Line the bottom and 2 sides of the pan with parchment paper. Spray again
In a medium bowl, sift the flour, baking powder, and salt. Set aside. Zest the lemons in one bowl. Squeeze the lemons for lemon juice in another bowl.
Using a mixer, beat the butter, oil, and sugar. Beat on high for 3 minutes. It should be very fluffy and light. Add in lemon zest, lemon juice, and sour cream. Mix until combined. Scrape the bowl.
Add in eggs one at a time and mix until combined.
Add in ⅓ of the dry ingredients and half of the buttermilk. Add in another ⅓ of the dry ingredients and the rest of the buttermilk. Mix. Then, add the rest of the dry ingredients. Scrape the bowl and mix for another 10 seconds.
Pour the cake batter into the pan. Bake for 40-48 minutes. Cake is done baking when a toothpick inserted comes out clean.
Let cake cool in pan for 10 minutes before transferring to a cooling rack. Allow cake to cool completely before frosting.