I like the idea of a polenta cake and it just so happens I was making Danishes the other day and filling them with a cheese and prune filling. I don't think polenta cakes are a stretch and have seen a few Italian recipes for them. I also think prunes and ricotta are a great combination. This cake is by no means sugary sweet. I call it an afternoon cake, something you might eat about 3 o'clock with a cup of expresso or Nocello, the Italian walnut liqueur. —thirschfeld
Preheat the oven to 425 degrees. In a mixing bowl combine the drained ricotta and butter and mix until blended. Add the flour, egg and sugar and mix to combine. Fold in the prunes and set aside.
Place the 4 tablespoons of butter into a 10 inch cast iron skillet. Set aside.
In a mixing bowl add the cornmeal, salt, baking soda, baking powder, zest and sugar. Stir with a whisk.
Add the milk and egg and whisk to combine. Set aside. This allows the cornmeal to hydrate.
Place the skillet with the butter in the oven and set a timer for 12 minutes. While you are waiting, in a small mixing bowl combine the remaing 1/3 cup of cornmeal, with the walnuts and butter and combine using your fingers to make a streusel.
When the timer goes off remove the skillet from the oven. Remember the handle will be smoking hot. Carefully pour in the cornmeal batter, it will start cooking immediately. Using a spoon or scoop carefully drop dollops of ricotta prune mixture over the top of the cornmeal batter. Now sprinkle the streusel evenly over the top. Using a towel or oven mit, the handle is still hot, place the skillet back into the oven and bake for 15 to 20 minutes. Remove from the oven and let cool, covered with a towel, for 15 minutes. Serve with expresso or Nocello.