Preheat your oven to 350°F (175°C). Grease two 9-inch round cake pans thoroughly and line the bottoms with parchment paper.
In a large mixing bowl, sift together the all-purpose flour, baking powder, baking soda, and salt. Set aside.
Using an electric mixer, cream the unsalted butter and granulated sugar together on medium-high speed until light and fluffy, about 4 to 5 minutes.
One at a time, add the eggs to the creamed butter mixture, beating well after each addition. Then mix in the vanilla and lemon extracts.
Alternately add the dry ingredients and the buttermilk mixed with sour cream into the butter mixture, starting and ending with the dry ingredients. Fold gently until just combined.
Fold in the finely grated lemon zest and fresh lemon juice carefully.
Divide the batter evenly between the prepared pans and smooth the tops with a spatula. Bake for 30 to 35 minutes, or until a toothpick inserted comes out clean. Cool in pans for 10 minutes, then transfer to wire racks to cool completely.