Blanch plums in boiling water for 10 seconds.
Peel and slice and set aside.
Beat eggs and sugar and then add milk, vanilla and flour and beat well.
Spray a 10" pie plate or shallow baking dish with nonstick cooking spray, pour in batter and top with plums.
Spread batter over and around plums with the back of a spoon.
Bake at 350° for 45 minutes to 1 hour, or until a knife inserted in center comes out clean.
Dust with powdered sugar and serve warm.