12 ripe Italian plums, pitted and halved
1 Tbs. Butter
1/4 cup sugar
1 cup flour
3/4 teaspoon baking powder
1/4 teaspoon baking soda
1/4 teaspoon salt
1/2 cup butter, softened at room temperature
2/3 cup sugar
1 large egg
2/3 cup sour cream
1 teaspoon pure vanilla extract
Preheat oven to 350 degrees. Butter an 8" by 8" glass baking dish. Cover the bottom with parchment paper (important!).
Melt 1 Tbs. of butter in a skillet over medium heat. Add the plums and 1/4 c. sugar. Toss and stir, gently, for approx. 5 minutes, or until the plums release their juice and make a lovely syrup. Arrange the plums in the bottom of the baking dish, cut side down. Pour the syrup over the plums.
In a bowl, whisk together the flour, baking powder, baking soda and salt. Set aside.
With an electric mixer beat 1/2 c. butter and 2/3 c. sugar until fluffy. Beat in the egg, sour cream and vanilla. Add the flour mixture, mixing until just incorporated. Don't over beat.
Spoon the thick batter over the plums and use a spatula to smooth it evenly. Bake for 45 to 50 minutes or until a toothpick comes out clean. Cool for one hour. Use a knife to loosen sides of cake from the baking dish. Place a plate on top of the cake and carefully invert it. The cake will eventually fall to the plate. Remove baking dish. Carefully peel off the parchment paper. Enjoy your delicious creation with a nice cup of coffee.