Heat oven to 350°F. Coat 2 8-inch cake pans with nonstick cooking spray. Line bottoms with waxed paper and spray again.
Blend cake mix, water, oil, eggs, cream of coconut and coconut extract in large bowl at low speed until just moistened, about 30 seconds. Beat at medium speed for 2 minutes. Divide batter between the prepared pans.
Bake in 350°F oven for 35 minutes or until toothpick inserted in center of the cake comes out clean. Allow to cool on a cooling rack for 15 minutes. Turn cakes out and remove waxed paper. Allow to cool completely.
In a large bowl, mix together powdered egg whites and 1/4 cup warm water and let stand for 5 minutes. Add cream of tartar and salt. Beat on medium-high speed until soft peaks form. Gradually beat in the sugar. Add coconut extract. Beat in half of the marshmallow creme and 1 tablespoon of water. Beat in remaining creme and 1 tablespoon water. Beat to good spreading consistency, adding 1 or 2 tablespoons of water as needed.
Place 1 cake layer on a serving plate. Spread with lemon curd. Top with second cake layer. Generously frost top and sides of cake with frosting. Press coconut onto sides and top of cake. Refrigerate for 1 hour before serving.