Preheat oven to 350°F. Grease and line one 9" or two 6" pans. Whisk together dry ingredients. Separately, whisk yolks and vanilla, and gradually whisk in warmed coconut milk. Separately, cream butter and sugar until fluffy. Alternate adding dry ingredients and egg yolk mixture until smooth. Beat egg whites to stiff peaks (adding cream of tartar when foams). Fold egg whites into batter. Bake 25min until toothpick comes out clean.