Step 1

Place the rack in the center of the oven and preheat to 350F. Spray 2 9-inch cake pans lightly with nonstick spray, then line the bottoms with parchment paper. Lightly spray the parchment paper. Place the cake pans on a baking sheet.

Step 2

In a medium bowl, sift together the flour, baking powder and salt. In another bowl, whisk together the milk and egg whites.

Step 3

In the bowl of a stand mixer, combine the sugar and the lemon zest. Using your finger, rub the zest into the sugar until it is moist and fragrant. Add the butter to the sugar mixture and beat until very light, 3 minutes. Beat in the lemon extract. Beating on medium speed, add one third of the flour mixture. Beat in half of the milk/egg mixture, then half of the remaining dry mixture. Add the remaining milk/egg mixture, followed by the remaining dry mixture, beating on medium the whole time. Beat for 2 minutes, making sure everything is thoroughly mixed and aerated. Divide the mixture between the two pans and smooth the tops with a rubber spatula.

Step 4

Bake in the preheated oven for 30-35 minutes, or until springy to the touch and baked through. Transfer to a cooling rack to cool for 5 minutes, then run a knife around the sides of the pan. Turn the cakes out onto a cooling rack and remove the paper liners. Cool to room temperature.

Step 5

Place the sugar and egg whites in a mixing bowl. Place the bowl over a pan of simmering water and whisk constantly. Whisk until it feels hot to the touch and the sugar is dissolved, about 3 minutes. The mixture should look like shiny marshmallow cream. Remove the bowl from the heat.

Step 6

With the whisk attachment (or a hand mixer), beat until it is cool, about 5 minutes. Switch to the paddle attachment. Add the butter, one stick at a time, and beat until very smooth. Once all of the butter has been incorporated, beat on medium-high speed until it is thick and very smooth, 6 to 10 minutes. The mixture may curdle or separate – just continue to beat until it comes together. With the mixer on medium, add the lemon juice gradually, and then the vanilla. The frosting should be shiny and velvety.

Step 7

Use a sharp serrated knife to slice each cake layer into half horizontally. Place one cake layer, cut side up, on a cake plate. Spread one-third of the preserves on the cake. Cover the jam with about one-quarter of the buttercream. Top with another cake layer, spread with one-third of the preserves and one-quarter of the buttercream. Repeat with a third layer, using the remaining preserves and another quarter of the buttercream. Place the last layer on top, cut side down. Use the remaining buttercream to frost the sides and top of the cake. Gently press the coconut into the frosting on the sides and top of the cake.