Preheat your oven to 350°F (175°C) and grease two 9-inch round cake pans.
In a bowl, whisk together flour, baking powder, and salt. Set aside.
In a large mixing bowl, beat butter and sugar until light and fluffy.
Add eggs one at a time, beating well after each addition.
Mix in lemon zest, lemon juice, and vanilla extract.
Alternately add the dry ingredients and buttermilk, mixing until smooth.
Divide the batter evenly between the prepared pans and bake for 25-30 minutes.
Check doneness with a toothpick—if it comes out clean, the cakes are ready.
Let the cakes cool completely before assembling.