Instructions

1. First, make the cake. Preheat the oven to 350°F. Line 2 8-inch round pans with parchment paper and grease the sides with cooking spray. Set aside.
   In the bowl of a stand mixer combine the sugar and key lime zest, rubbing the zest into the sugar with your fingers. Add the butter and oil to the bowl and beat with the whisk attachment, on low speed until combined so the oil doesn’t fly everywhere. Gradually increase the speed to medium-high and beat until smooth, about 3 minutes.
2. Use a silicone spatula to scrape down the sides and bottom of the bowl, then add the eggs and vanilla. Beat on medium-high speed until the mixture is light and fluffy, about 2 minutes.
3. In a small bowl combine the milk and key lime juice. Stir and set aside.
4. In a separate mixing bowl, whisk together the flour, baking powder, and salt. With the mixer on low speed, alternate adding in the dry ingredients and the milk and key lime juice. in 3 additions (you’ll add half the dry, then all of the wet, then the other half of the dry). It’s okay if the batter still has a few lumps in it–you don’t want to overmix.
5. Divide the cake batter evenly between your prepared pans, using the spatula to spread the batter into a flat, even layer. Bake until the cake has risen, the top springs back to the touch, and a butter knife inserted in the center of the cake comes out clean, 30 to 40 minutes.
6. Place the cakes on a cooling rack and allow them to cool slightly. To remove from the pan, drag a butter knife around the edge of the cake, then carefully flip the cakes out onto a cutting board, peel away the parchment paper, and re-invert it, right-side up onto a cooling rack to cool completely.
7. Once the cake has cooled, make the key lime syrup. Combine the key lime juice and sugar in a microwave safe bowl and microwave on high for 1 minute. Stir until the sugar is melted completely into the juice. Set aside to cool.
8. Next make the graham cracker filling. Combine the graham cracker crumbs, melted butter, sugar, honey, key lime juice and salt in a medium mixing bowl and stir to combine.
9. Next, make the frosting. In a stand mixer fitted with the whisk attachment, cream together the butter and cream cheese until completely smooth, about 45 seconds. Add the powdered sugar and beat on low speed gradually increasing to high until smooth. Add the vanilla, key lime zest and salt, and beat to combine. Scrape down the bowl and transfer about ⅓ of the frosting to a piping bag for the center layer of the cake.
10. Assemble the cake. Place the first cake down on a cake stand to serving plate and generously soak the top with the key lime syrup. Pipe frosting all over the top of the cake, making a large border around the edge of the cake so that the center is lower and the sides come up high. Spread the graham cracker mixture into an even layer within the frosting border.
11. Place the second cake on top of the first and generously soak the top with the key lime soak. Use the rest of the frosting to frost the top and sides of the cake. Top with thinly sliced key limes to garnish and place in the fridge until ready to serve!