Unsalted butter, for the pan
1 cup all-purpose flour, plus more for dusting
1 1/2 cups granulated sugar
1 teaspoon baking powder
3/4 teaspoon baking soda
1/4 teaspoon salt
4 large eggs, separated, plus 2 egg whites, all at room temperature
1/2 cup vegetable oil
1/2 cup coconut milk, at room temperature
1 1/2 teaspoons coconut extract
Pinch of cream of tartar
Confectioners' sugar, for dusting
1 tablespoon white rum
6 large egg whites, at room temperature
1 cup plus 2 tablespoons granulated sugar
3 sticks unsalted butter, at room temperature, cut into pieces
3 tablespoons white rum
4 cups sweetened shredded coconut