One layer of this coconut cake and another layer of Banana Cake surrounded by cream cheese frosting and colored coconut flakes comprise the very special Alexis' Heart Cake.
Preheat oven to 350 degrees. Butter a 10-inch heart-shaped cake pan; line bottom with parchment paper. Butter parchment and dust with flour, tapping out excess; set aside.
In a large bowl, whisk together flour, baking powder, and salt. Place shredded coconut in the bowl of a food processor; pulse until finely chopped. Stir chopped coconut into flour mixture until combined; set aside.
In the bowl of an electric mixer fitted with the paddle attachment, beat together butter and sugar until light and fluffy, about 4 minutes, scraping down the side of the bowl as needed. Add whole eggs, egg whites, and vanilla; beat until fluffy and combined. With the mixer on low speed, add the flour mixture, alternating with the coconut milk, beginning and ending with the flour mixture, mixing well after each addition.
Pour batter into prepared pan; smooth with an offset spatula. Bake, rotating pan halfway through, until cake is golden brown and a cake tester inserted into the center comes out clean, about 55 minutes.
Transfer pan to a wire rack to cool for 30 minutes. Invert cake onto rack; peel off parchment paper. Reinvert cake and let cool completely, top side up.