This polenta-based “pizza pie” is a fresh, delicious mash-up of a casserole and a pizza. It’s a fun take on a classic party dish. The polenta crust needs to chill for an hour in the refrigerator, but can be prepared a couple of days in advance.
1. To prepare the crust, line the sides of two 8-inch round baking pans with strips of parchment paper. Set aside.
2. In a large saucepan, combine 8 cups water with the cumin; bring to a boil. Add the polenta in a slow stream, whisking continuously to prevent lumps from forming. Add the flaxseed, turmeric (if using), and salt to taste. Cook over medium-high heat until the mixture starts to bubble. Cover the pan, reduce the heat to medium, and simmer 15 to 20 minutes, or until the polenta has absorbed all the water and reached a spreadable consistency.
3. Divide the polenta evenly between the two prepared pans. Keeping the parchment paper in place, spread the polenta in the pans, making the edges a bit higher than the center. Let cool to room temperature, and refrigerate for at least 1 hour. The crust can be prepared a couple of days in advance; if refrigerating for more than an hour, cover in plastic wrap.
4. While the crust chills, prepare the sauce: Place the tomatoes, onions, garlic, marjoram, thyme, rosemary, oregano, and black pepper in a large saucepan. Cover and cook over medium-low heat for 30 minutes. Add the tomato paste, vinegar, and salt to taste. Cook, uncovered, until the sauce thickens and the water evaporates, about 20 minutes. Set aside.
5. To prepare the topping, cook the mushrooms in a dry skillet over medium heat, stirring occasionally, until mushrooms are soft and the liquid they release is almost completely evaporated, 5 to 7 minutes. Add the zucchini and cook for 5 minutes. Remove from the heat and set aside.
6. Remove the polenta crusts from the refrigerator, and let them stand for 20 minutes to bring them to room temperature. Preheat the oven to 350°F.
7. In s saucepan, cook the bell peppers over medium heat until softened and the liquid they release has evaporated, about 10 minutes. Add the nutritional yeast, and cook for 1 minute. Transfer the mixture to a small plate to cool. Just before use, mix in the chopped basil.
8. Spread half the pizza sauce on each crust. Spread the mushrooms and zucchini evenly on top. Sprinkle with the bell pepper and basil mixture. Bake until heated through, about 30 minutes. Slice and serve hot. For extra cheesy flavor, sprinkle nutritional yeast on top.