Upside-Down Blueberry Puffs Brunch

Preheat oven to 375 degrees.Wash blueberries and pat dry.Spray six 6-ounce custard cups with baking spray.Divide blueberries among custard cups, reserving 6 to top cakes.Combine flour, salt and baking powder in a mixing bowl and set aside.Beat egg white until foamy; add cream of tartar and beat until stiff peaks form. Set egg white aside.Cream butter; gradually add sugar and continue creaming until light.Add eggs and vanilla; mix until well blended.Add flour mixture, alternating with milk, to butter mixture and beat until well combined. Batter will be thick.Gently fold beaten egg white into flour/butter mixture.Spoon batter into custard cups over berries, filling no more than full.Place custard cups on a baking sheet; bake for 30 minutes or until cakes test done by inserting a toothpick near center.Turn out cakes directly from oven on wire racks.Serve warm or at room temperature. If desired, serve with whipped cream or ice cream topped with a blueberry.