Preheat oven to 350 degrees Fahrenheit.

Grease the bottoms and sides of two 9-inch cakes pans. Place a parchment circle in the bottom of each pan, grease the parchment and lightly dust both cakes pans with flour. Set aside.

In a large bowl, sift together cake flour, baking powder and salt and whisk to combine. Set aside.

In the bowl of a stand mixer, cream butter and sugar until light and fluffy, 5-7 minutes. Scrape down the bowl and add egg whites and egg, one at a time, beating after each addition. Add extracts and mix to combine.

Scrape down bowl and alternate adding flour mixture and buttermilk, beginning and ending with the flour.

Divide batter evenly among prepared cake pans and spread out in a neven layer. Bake in preheated oven for 30-35 minutes, or until a toothpick inserted into the center comes out clean except for a few moist crumbs.

Allow cakes to cool in the pan for 10 minutes, then remove cakes from pans and transfer to a wire rack to cool completely.

Once the cakes are room temperature, place the butter in a clean stand mixer bowl and beat until fluffy. Scrape the bowl and turn mixer on low. Mix in the lemon juice, then add the powdered sugar one cup at a time, beating to incorporate.

After adding powdered sugar, add buttermilk and mix to beat out any clumps. Mix in 1 drop of yellow food color if desired. Check the consistency of the frosting. If it is too loose, add another 1-2 cups of powdered sugar and beat until smooth.

Add second cake and gently press the cake a little to level the top. Then scoop all remaining frosting on top of the cake. Use the spatula to work the frosting over the top and down the sides.

To create the "swirl" pattern, gently press tip of spatula down in the center of the cake and continuously turn cake stand while working spatula outward. Do the same around the side, working spatula from top to bottom of cake. Clean up any frosting around the bottom with a damp paper towel.

Slice and enjoy!