Make the frosting: Whisk the egg whites and sugar in a heatproof bowl set over a saucepan of simmering water (do not let the bowl touch the water) until the mixture is warm and the sugar dissolves, 3 to 4 minutes. Remove the bowl from the pan and beat with a mixer on medium-high speed until stiff, glossy peaks form, 6 to 8 minutes. Beat in the almond extract, then beat in the butter a few pieces at a time. Continue beating until the frosting is smooth, 1 to 2 minutes. (Don't worry if the mixture looks separated at first; keep beating and it will come together.)

Assemble the cake: Bring the honey and 2 tablespoons water to a gentle simmer in a small saucepan over medium heat; let cool slightly. Place 1 cake layer on a platter; brush with half of the honey mixture and spread the apple butter on top, stopping about 1/2 inch from the edge. Top with the second cake layer and press down gently; brush with the remaining honey mixture. Cover the whole cake with the frosting and top with sliced almonds.

Photograph by Levi Brown