"Easy and beautiful cake to make with ingredients you have on hand. Great to take to a party or picnic. Use a cake plate that is wider than the cake; the berries and juice run down the sides, but it is gorgeous when done!"
2Melt brown sugar and 2 tablespoons butter together in a saucepan over medium heat. Add blackberries to brown sugar mixture; cook and stir until mixture bubbles, 1 to 3 minutes. Stir 3/4 cup white sugar into berries, crush berries slightly with a fork, and continue cooking until berries are hot and slightly broken-down, about 5 minutes more; remove from heat and pour into a 9-inch cake pan.
3Beat 1 cup white sugar and 1/2 cup butter together in a bowl with an electric mixer until light and fluffy; beat in eggs.
4Whisk flour, baking powder, and salt together in a bowl. Alternately stir flour and milk into butter mixture, beginning and ending with the flour mixture. Mix vanilla into batter.
5Pour batter over blackberry mixture in the 9-inch cake pan.
6Bake cake in the preheated oven until cooked through, 35 to 40 minutes. Let cake cool in the pan until warm, but not completely cooled, about 30 minutes. Run a knife along the inside edge of the pan to separate cake from the sides, place a cake plate over the top of the pan, and flip the pan. Lift the pan slowly to release the cake from the pan.
Footnotes
Cook's Note:
Instead of heating the brown sugar, butter, and blackberries together in a saucepan, I heat them directly in the cake pan on the stove.