Preheat the oven to 350F degrees. Butter and flour a 9x13 inch baking pan.
Whisk together the flour, baking powder, baking soda, and salt in a large bowl.
In a large bowl beat the egg whites until stiff peaks form - set aside.
Mix together the coconut milk and sour cream in a liquid measuring cup or small bowl.
In a large bowl using an electric mixer, beat the butter and sugar until fluffy. Then mix in the egg yolks, coconut extract and vanilla extract.
Mix about ½ of the coconut milk and sour cream into the butter mixture, followed by about ½ of the dry ingredients. Repeat with the rest of the coconut milk and sour cream, and dry ingredients.
Gently fold the egg whites into the batter, about ½ at a time.
Pour the batter into the prepared pan and bake for 30-35 minutes or until an inserted toothpick comes out clean.
Allow to cool.