Prepare the Cake Layers: Preheat oven to 325°F. Coat 3 (8-inch) round cake pans with baking spray, and set aside. Beat butter with a stand mixer fitted with a paddle attachment on medium speed until creamy, about 1 minute. Gradually add sugar, beating until light and fluffy, 3 to 4 minutes. Add lemon zest (if using), vanilla, and coconut extract; beat just until combined, about 30 seconds.

Sift together cake flour, baking powder, and salt in a medium bowl. Add to butter mixture alternately with milk, beginning and ending with flour mixture, beating on low speed just until combined after each addition.

Beat egg whites with an electric mixer on high speed until stiff peaks form (don’t overbeat, or they will be dry), about 2 minutes. Fold about one-third of beaten egg whites into cake batter; fold in remaining egg whites in 2 additions. Spoon batter evenly into prepared cake pans (about 2 ⅓ cups batter per pan).

Bake cakes on middle rack in preheated oven until a wooden pick inserted in center of cakes comes out clean, 23 to 25 minutes. Cool in pans on wire racks 10 minutes. Remove cakes from pans; place directly on wire racks. Cool completely, about 1 hour. 

Meanwhile, prepare the Coconut Cream Frosting: Beat butter and cream cheese with an electric mixer on medium speed until creamy, about 2 minutes. Gradually add powdered sugar, beating on low speed until combined, about 1 minute. Increase mixer speed to medium-high; gradually add cream of coconut, vanilla, and coconut extract, beating until smooth and fluffy, about 2 minutes.

Transfer 3 tablespoons of the frosting to a small bowl; stir leaf green food coloring to reach desired shade of green. Spoon into a piping bag fitted with a small round tip. Transfer 1 tablespoon of the frosting to a separate small bow; stir in super red food coloring to reach desired shade of red. Spoon into a piping bag fitted with a small round tip. Let remaining frosting stand, covered, at room temperature until ready to use or up to 1 hour.

Assemble the cake: Place 1 layer on a serving plate or a cake stand. Spoon 1 cup Coconut Cream Frosting into a ziplock plastic bag. Snip a ½-inch tip off 1 bag corner. Pipe a ring of frosting just inside the top edge. Spread with half of desired filling (if using the Whipped Chocolate Ganache Filling, spread with 1 cup filling), spreading to edge of piped frosting. Repeat process once with 1 additional Cake Layer, frosting, and filling. Top with remaining layer. (If using ganache filling, reserve any remaining for another use.) Spread cake top and sides with a thin layer of the remaining frosting. Refrigerate, uncovered, 1 hour. Spread remaining frosting over top and sides of cake. Gently pat coconut around bottom edge of cake and about 1 inch up sides. Sprinkle coconut on top of cake. Pipe green frosting in a garland pattern around sides of cake; pipe red frosting on garland to resemble berries. Insert Peace Dove Cookies into top of cake.