Preheat oven to 350 degrees. Butter and flour two - 9 inch x 1 1/2 inch cake pans, and then line the bottoms with parchment paper (or spray with Bakers Joy).
Separate eggs while still cold, and bring to room temperature.
Sift flour, baking powder, baking soda, salt together. Set aside.
Cream butter for two minutes until fluffy.
Cream butter with sugar for 2-minutes.
Add egg yolks one at a time. Beat each for 45 seconds, medium speed.
Add vanilla, mix. Add coconut.
Turning mixer to low speed, add flour mixture and buttermilk, alternating, beginning and ending with flour mixture.
In separate clean bowl whip egg whites until foamy. Add cream of tartar until soft peaks are formed. Beat until stiff peaks are formed.
Gently fold in to cake batter with a spatula.
Bake at 350 for 35-40 minutes.
You can do a two layer cake or a four layer cake, by cutting the layers in half. Or use three cake pans for a triple layer, dividing the cake evenly.
Adjust baking time accordingly.
Allow cakes to rest on a rack for ten minutes before removing.
Invert cakes and allow to completely cool before frosting. I usually freeze cakes for ten minutes before frosting.
Cream butter until it's fluffy.
Add confectioner's sugar one cup at a time. Between each cup add a little cream. Add vanilla at the end.
To frost cakes, freeze cakes for ten minutes. Remove and beginning with each layer, lightly spread a dry crumb layer. Let that set up and then frost each layer. Add coconut to frosting between each layer. Completely frost cake, and add coconut to cover cake entirely.
Serve at room temperature.
If you need to refrigerate, take out at least one hour in advance.