Ube Cake Filipino Purple Yam Cake

Name: Ube Cake Filipino Purple Yam Cake
Ingredients: 2 ½ cups sifted cake flour; 2 ½ tsp baking powder; ½ tsp salt; 2 tsp ube extract; ½ cup vegetable oil; ½ cup milk, room temperature; 8 large egg yolks, room temperature; ⅓ cup granulated sugar; 3.5 oz ube jam (about ½ cup), room temperature; Purple gel food color (optional); 8 large egg whites, room temperature; 1 tsp cream of tartar; ¾ cup granulated sugar; 5 large egg whites; 1 cup granulated sugar + 2 tablespoons; Pinch of salt; 2 cups unsalted butter, cut into parts, room temperature; 1 ½ tsp vanilla extract; Ube extract to taste