Preheat the oven to 350 degrees. Spray 3 6 inch cake pans with non stick spray and line the bottoms with parchment paper.
In a medium bowl, whisk together the cake flour, baking powder, baking soda and salt. Then set aside the dry ingredients.
2 ½ cups (280 g) cake flour, ¼ teaspoon baking soda, 1 ½ teaspoon baking powder, ½ teaspoon salt
In a large mixing bowl, cream together the butter and granulated white sugar with an electric hand mixer on high speed until fluffy, about 3-4 minutes. (If using a stand mixer, use the paddle attachment.)
10 tablespoon (140 g) unsalted butter, softened, 1 ½ cups (300 g) granulated white sugar
Then add in the egg whites, vanilla and coconut extract and mix on medium-high speed until smooth and pale in color, about 2-3 minutes. Scrape the sides of the bowl with a rubber spatula as needed.
6 egg whites, at room temperature, 2 teaspoon vanilla, 2 teaspoon coconut extract
Add in the coconut milk and sour cream and mix on medium speed just until combined.
1 cup (240 ml) canned, full fat coconut milk (unsweetened), ½ cup (122 g) sour cream
Add in the dry ingredients a little at a time. Mix on low then medium speed just until the batter is combined and smooth, scraping the sides of the bowl as necessary.
Divide the batter evenly among the cake pans. Bake the cakes for 28-32 minutes, or until a toothpick comes out clean from the centers.
Let the cakes cool in the pans for 10 minutes, then transfer to a cooling rack to completely cool.