Step 1

Preheat the oven to 350 degrees F. Grease an 8-inch square baking pan.

Step 2

Whisk together the flour, cornmeal, baking powder and salt in a large bowl. Whisk together the milk, yogurt, vanilla, eggs and 1 cup of the sugar in a separate bowl. Add the egg mixture to the flour mixture, stirring just until combined. Fold in 1 cup of the blackberries.

Step 3

Pour the batter into the prepared pan. Bake until a toothpick inserted in the center comes out clean, 35 minutes. Let the cake stand in the pan for 10 minutes. Use a wooden skewer to poke holes in the cake.

Step 4

Meanwhile, mash about 1/2 cup of the remaining blackberries and place in a bowl with the remaining whole blackberries and set aside. Put the lavender and remaining 3 tablespoons sugar in a small bowl. Let stand until the blackberries begin to become syrupy, 15 minutes. Spoon the blackberry syrup over the warm cake and let cool.