This recipe is wonderful as holiday pupu or nice main course paired with a crisp green salad and sparkling beverage.
Prepare polenta according to the package instructions. Pour warm polenta over parchment lined baking sheet to a 1" thickness; smoothing top flat with a spatula. Let cool.
In a medium-large skillet, sauté onions in olive oil until soft; add in the garlic, Italian seasoning, pepper or chili flakes and salt and cook for a few minutes. Then add in your desired vegetables, sauté til crisp tender, about 3 to 5 minutes. Remove from the pan.
Add in the spinach and cook until wilted. Cool then squeeze out the excess liquid and chop.
In medium pot heat marinara sauce to a slow simmer and reduce to thicken; about 10 minutes.
Slice polenta into large squares and pan fry on both sides (non stick or cast iron works well) until lightly browned and crisp. Place on a parchment lined baking sheet.
Pour marinara sauce over polenta squares then top with spinach and sautéed vegetables. Add olives, fresh basil and Parmesan if using. Bake at 350° for 20 minutes or until just heated through.