Yogurt Plum Cake with Lemon and Cornmeal

Preheat the oven to 350°F. Prepare a 9-inch round cake pan by spraying the bottom and sides with cooking spray and then lining the bottom with parchment paper.
In a medium bowl, combine the sliced plums, ¼ cup brown sugar, 1 tablespoon lemon zest, and 1 tablespoon flour. Stir everything together well and set aside.
In a large microwaveable bowl, melt the butter. Add the ½ cup brown sugar, oil, eggs, vanilla, yogurt, lemon juice, and zest. Whisk until well combined.
Sprinkle the remaining flour, corn meal, and baking soda over the wet ingredinets. Whisk the dry ingredients into the wet ingredients until just combined.
Pour the cake batter into the prepared pan and smooth it into an even layer.
Stir the plum topping again and distribute the plums evenly over the top of the cake batter. Drizzle any accumulated juices over the top of the cake.
Bake the cake for 42-45 minutes, or until a toothpick inserted into the center of the cake comes out clean (be sure to pick a spot in the cake that the toothpick won't go through a plum).
Run a knife around the edge of the cake and allow it to cool for 15 minutes.
Run the knife around the edge of the cake pan again and invert the cake over a wire cooling rack. Flip the cake back over again onto a serving platter or large plate.
Allow the cake to cool for another 15 minutes and then slice with a serrated knife for the cleanest cuts. Dust slices with powdered sugar and dollop with whipped cream.