Preheat your oven to 350°F (175°C) and prepare three 8-inch cake pans by greasing them with unsalted butter, dusting them with flour, and lining the bottoms with parchment paper.

In a large mixing bowl, combine the flour, sugar, baking powder, baking soda, and salt using a whisk.

Add the softened butter to the dry mixture and blend until the mixture resembles sandy crumbs.

Pour in the oil and lime zest, mixing until everything is well combined.

In a separate measuring cup, whisk together the lime juice, whole milk, eggs, and vanilla until smooth.

Slowly pour the wet ingredients into the dry mixture while mixing on low speed until just combined.

Divide the batter among the prepared pans and bake for 26-28 minutes or until a toothpick comes out clean.

Allow the cakes to cool in the pans for 10-15 minutes then invert onto a cooling rack.

To prepare the curd, whisk together the egg yolks, lime juice, sugar, and salt in a saucepan over medium heat until thickened.

Remove from heat, add butter, and stir until smooth.

For the frosting, beat the softened butter and cream cheese until creamy, then add powdered sugar and mix, folding in the cooled key lime curd.

Assemble the cake by leveling the cakes, frosting between layers, and smoothing frosting on the sides and top.

For decoration, sprinkle graham cracker crumbs and lime zest on top, then chill the cake for at least 30 minutes before serving.