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1
Heat 1 tablespoon olive oil in a saucepan over medium heat. Add garlic and red pepper flakes; cook and stir until golden, about 1 minute. Stir in basil and oregano; cook until fragrant, about 1 minute. Stir in tomato sauce. Simmer sauce until flavors combine, about 20 minutes.
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2
Combine spinach and 2 tablespoons water in a large skillet over medium heat. Cover and cook until spinach is wilted, 3 to 5 minutes. Drain and cool until easily handled, about 5 minutes. Gather spinach into a ball and squeeze out excess water. Chop coarsely.
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3
Combine chopped spinach, ricotta, and 1/2 cup Parmesan cheese in a bowl.
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4
Preheat oven to 400 degrees F (200 degrees C). Line 2 baking sheets with parchment paper.
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5
Divide eggplant, red bell pepper, and orange bell pepper between lined baking sheets. Drizzle with 2 tablespoons olive oil and toss to coat. Season with salt and pepper.
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6
Roast in the preheated oven, stirring every 10 minutes, until tender and browned in spots, about 30 minutes. Remove from oven.
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7
Bring 6 cups water to a boil; add salt. Pour in polenta in a steady stream, whisking constantly. Reduce heat to low. Whisk until polenta thickens, about 5 minutes. Cover and cook, stirring vigorously every 10 minutes, until polenta is the consistency of porridge, about 30 minutes.
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8
Reduce oven temperature to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish with cooking spray.
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9
Spread half the polenta evenly in the bottom of the baking dish. Layer half of the spinach mixture, roasted vegetables, and sauce on top. Top with 1/2 cup mozzarella cheese and 1/4 cup Parmesan cheese. Repeat layers with remaining polenta, spinach mixture, roasted vegetables, and sauce. Top with remaining mozzarella cheese and Parmesan cheese.
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10
Bake in the preheated oven until cheese melts and sauce is bubbly, about 20 minutes. Let cool before cutting so layers hold, at least 20 minutes.
