Preheat oven to 350 F. Prepare three 3-inch-by-6-inch disposable paper mini-loaf pans for baking; you can also use them for packaging the cakes as gifts. Spray inside of loaf pans with cooking spray, and place on a baking sheet. Set aside. For the cake: In the bowl of a stand mixer, blend 2 sticks butter, sugar and sour cream until light and fluffy, about 3–4 minutes. Add eggs, one at a time, beating thoroughly after each addition. Add vanilla and lemon extracts, and continue beating until combined.