Adjust an oven rack to the middle position and preheat to 350ºF/176ºC. Prepare three 3 6-inch round cake pans with cake goop, parchment paper, or another preferred pan release. Making sure to coat the bottom and sides of the pan. Spread your coconut flakes evenly onto a cookie sheet pan.
Broil the coconut flakes on high for 2-3 minutes or until they just begin to turn brown around the edges. Stir the coconut and broil for 1-2 minutes more until lightly golden. Watch it closely because it can burn quickly. Remove it from the oven and let it cool.
Whisk together the flour, baking powder, baking soda, and salt in a medium bowl. Set the dry ingredients aside.
Heat the coconut oil in a small bowl in the microwave until it is very soft and beginning to melt, but not hot.
Add the coconut extract and vanilla extract to the room-temperature buttermilk.
Add the butter and coconut oil to a stand mixer with the paddle attachment and beat at medium-high speed until smooth and shiny, about 30 seconds.
Gradually sprinkle in the sugar, and beat until the mixture is light and fluffy, about 3-5 minutes.
Add the egg yolks one at a time to the mixture, combining after each.
With the mixer on low speed, add about a third of the flour mixture to the batter, followed immediately by about a third of the milk, mix until the ingredients are almost incorporated into the batter.
Repeat the process 2 more times. When the batter appears blended, stop the mixer and scrape the sides of the bowl.
Carefully fold in the toasted coconut until it’s all combined.
Place the egg whites in a mixing bowl with the whip attachment. Whip on medium-high speed until it's foamy.
Add in the cream of tartar and whip until semi stiff peaks form.
Fold in the whipped egg whites carefully into the cake batter, and try not to beat out too much of the volume in the egg whites.
Divide the cake batter evenly between 3 6-inch cake pans or 2 8-inch pans.
Bake for 30-35 minutes until a skewer inserted comes out clean.
Transfer the pans to a wire rack and let them cool in the pans for 10 minutes.
Invert the cakes onto a cooling rack and cool completely before frosting. I like to flash freeze them for 30 minutes if I’m using them right away, or wrap them in plastic and freeze them overnight. Pro-Tip: Wrapping your cakes while warm and then freezing them will lock in the moisture.