Preheat the oven to 325°F. Coat an 8-inch round cake pan with nonstick cooking spray and set aside.

In a small bowl, whisk the flour with the cornmeal until just combined. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, cream the butter with the sugar, salt, and honey until pale and fluffy, about 5 minutes. Add the eggs, one at a time, incorporating fully before adding another. (The batter may start to separate for the last few eggs.) Using a rubber spatula, fold the flour mixture into the butter mixture until just combined.

Pour the batter into the prepared cake pan and sprinkle the blackberries all over the top of the batter.

Bake for 35 minutes or until golden brown and a skewer inserted into the center of the cake comes out clean.

Cool the cake slightly, then remove from the pan, slice, dust with powdered sugar if desired, and serve.