Preheat oven to 350 degrees. Prep 3 x 6 inch cake pans by buttering them, lining the bottoms with rounds of parchment paper, then dusting them with flour and tapping out the excess.
Beat the butter and sugar until pale and fluffy, then add the eggs one at a time, beating to combine, about 2 minutes.
Sift the flour, baking powder, and salt together in a bowl and set aside. Mix the sour cream, milk, vanilla extract, lemon extract, and lemon zest together and set aside.
Stop the mixer, add the dry ingredients in 3 additions, alternating with the sour cream mixture and mixing gently between additions. Mix just until combined or finish by hand with a wooden spoon or spatula.
Distribute the batter evenly into the prepared pan and smooth with a spatula or the back of a spoon. Bake for 20 minutes, then rotate the pans in the oven and bake for an additional 10 or so minutes, checking every 3 minutes for doneness. A toothpick inserted into the center of the cake should come out clean and the top should spring back to the touch. Place on cooling racks until the pans are cool enough to handle, then run a knife around the edges of the cake to loosen it and turn it out onto the cooling racks to come to room temperature.
Assembly// Level the cakes if desired. Place the first layer face up on a cake board or serving plate. Pipe a ring of buttercream (buttercream in a ziplock with a corner snipped works perfectly here!) around the edge of the cake layer and fill it with lemon curd. Place the second layer on top and repeat. Place the last layer face down so the smooth side is up and press gently to secure. Place the cake in the fridge for a few minutes to firm up the buttercream and make icing the cake easier. Roughly ice the top and outsides of the cake. Decorate with flowers, dried lemon slices, or as desired. Serve at room temperature. May be refrigerated for up to 3 days.
Recipe by oh honey bakes at https://ohhoneybakes.com/lemon-butter-cake/