Plum Upside-Down Pudding Cake

Juicy aromas of plum and vanilla are combined in this delicious cake "upside down". The texture of this pie is given by the pudding, not the icing, so the plum flavor shines through the subtle sweetness, and the natural color of the plums adorns the magnificent top. Use red or black with the addition, depending on your preferences.
Combine the plums, 1 tablespoon sugar, lemon juice, and 1/4 teaspoon kosher salt in a bowl, stirring gently.Brush the sides and bottom of a 9-inch cast-iron skillet or deep pie dish. Lay out the bottom with plum slices, slightly overlapping each other.Whisk together the eggs, remaining sugar, buttermilk, vanilla and butter until smooth.Combine flour, baking powder, and remaining 1/2 teaspoon kosher salt; whisk with egg mixture. Pour the batter over the fruit. Bake at 375 ° C for 20-25 minutes or until golden brown. Let cool in the pan for about 30 minutes.Run the tip of the knife along the edge of the pie to loosen. Flip onto a platter and serve with sweetened whipped cream.