1. Preheat and Prepare the Pans:

– Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or line them with parchment paper circles for easy removal.

2. Mix Dry Ingredients:

– In a medium bowl, sift together the flour, baking powder, and salt. Set this aside.

3. Cream the Butter and Sugar:

– In a large mixing bowl, cream the butter and sugar together until light and fluffy. This should take about 3-5 minutes with a hand mixer or stand mixer on medium speed.

4. Add Eggs and Flavoring:

– Add the eggs, one at a time, beating well after each addition. Then, stir in the vanilla extract, key lime juice, and key lime zest.

5. Combine Dry Ingredients with Wet Ingredients:

– Gradually add the dry ingredients into the wet ingredients in three parts, alternating with the buttermilk. Start and end with the flour mixture. Mix just until combined; avoid overmixing to keep the cake fluffy.

6. Bake:

– Divide the batter evenly between the two prepared pans. Smooth the tops with a spatula.

– Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.

7. Cool the Cake:

– Let the cakes cool in their pans for 10 minutes, then transfer them to wire racks to cool completely.

8. Make the Frosting:

– While the cake cools, make the frosting. Beat the cream cheese and butter together until smooth. Gradually add the powdered sugar, 1 cup at a time, until smooth and fluffy.

– Add the key lime juice, lime zest, and a pinch of salt, mixing until everything is well combined.

9. Frost the Cake:

– Once the cakes have cooled completely, place one layer on a serving platter. Spread a generous amount of frosting over the top.

– Add the second cake layer and frost the top and sides of the cake evenly.

10. Garnish (Optional):

– For a decorative touch, garnish with extra lime zest or thin lime slices.