Mix flour, sugar, baking powder, salt on low.
Add room temperature butter to coat the flour.
Incorporate egg yolk and egg.
Add 1.5 teaspoons of vanilla.
Prepare the batter to be topped with sliced plums.
Ensure plums are ripe but not too soft.
Sprinkle 2 tablespoons of sugar on top.
Bake in a low oven at 325°F for over an hour.
