For a tropical twist on the classic Funfetti cake, use a food processor to combine flour, sugar, baking powder, and salt. Add in coconut oil, eggs, vanilla extract, coconut milk, and shredded coconut, and pulse until the batter is smooth. Fold in rainbow sprinkles, then bake in a preheated oven for 25-30 minutes. Let cool before frosting with a coconut buttercream made with coconut milk and powdered sugar.