Preheat oven to 350F and grease cake pans with cooking spray, set aside.
In a large bowl, combine the flour, baking soda, baking powder, and salt.
Using a stand mixer, cream the butter and sugar until light and fluffy.
Add the egg whites and vanilla and mix into the batter.
Gradually beat in the flour ingredients until combined
Beat in the lime juice, tequila, and lime zest.
Divide the batter between the 3 8" cake pans
Bake for 45-50 minutes or until a toothpick comes out clean.
Allow the cakes to cool completely.
Frosting
Using a stand mixer, beat the butter, and shortening into the mixer and beat until combined, smooth, and stiff with peaks
Spoon 1 cup of frosting into the piping bag and set aside (this will be for piping the swirls).
Decorating directions
Remove the domes from the cakes with a cake leveler to make them flat and even.
Place one cake round onto the cake board.
Scoop 1 cup of frosting onto the cake and smooth it evenly.
Place the second cake round onto the top of the frosting.
Scoop another cup of frosting onto the second cake layer and smooth evenly.
Place the last cake round onto the top of the frosting.
Using the remaining frosting, frost the entire cake.
Pipe dollops of frosting onto the top of the cake using the frosting you set aside earlier. I used a Wilton 1M and swirled it, starting in the center and moving out.
Add lime slices onto the frosting and zest a lime.
Place into the fridge for an hour to allow the frosting to harden up a bit.
Cut into slices and enjoy!
Notes
This makes a lot of cake. The photo shows 8 slices, but I would suggest piping it to at least 10 slices. Even that will be a lot. It's a tall cake, trust me - you get a lot.If you don't have sweet cream butter, regular unsalted butter will be more than fine.