Preheat the oven to 350℉. Spray a 9X9-inch cake pan with baking spray. Line the bottom and 2 sides of the pan with parchment paper and spray again.
In a medium bowl, sift the flour, baking powder, baking soda, and salt together. Set aside.
2 1/2 cups All-purpose flour, 1 1/2 tsp Baking powder, 1/2 tsp Baking soda, 1/2 tsp Salt
Using a mixer, beat the butter, oil, and sugar on high speed for 2 minutes. Scrape the bowl using a rubber spatula.
1/2 cup Unsalted butter, 2 TBSP Oil, 1 cup White granulated sugar
Add in lemon zest, lemon juice, and sour cream. Mix on medium until combined. Add in the eggs and mix on medium until combined. It will look split, but that it just because of the acid from the lemon.
2 Large lemons zested, 2 TBSP Lemon juice, 1/4 cup Sour cream, 3 Large eggs
Add in half of the flour and half of the buttermilk and mix on low speed until almost combined. Then, add in the the rest of the flour and buttermilk and mix on low speed until combined.
3/4 cup Buttermilk
Pour cake batter into the pan. Bake for 40-45 minutes. Bake until a toothpick inserted it comes out clean.