Preheat oven to 350°F. Lightly coat a 9-by-13-inch broiler-safe baking dish with cooking spray. Heat 1 tablespoon oil in a large skillet over medium-high heat. Add mushrooms, onion and bell pepper; cook, stirring occasionally, until the mushroom liquid has cooked off and the vegetables are tender, about 8 minutes. Add sun-dried tomatoes, garlic, ½ teaspoon salt and crushed red pepper; cook, stirring constantly, until fragrant, about 1 minute. Transfer the mixture to a medium bowl. (Do not wipe the skillet clean.)

Add the remaining 1 tablespoon oil to the pan; heat over medium-high heat. Add spinach; cook, stirring occasionally, until wilted, about 2 minutes. Transfer to a clean kitchen towel and let cool for 5 minutes. Gather the towel and squeeze firmly over the sink to remove as much liquid as possible. Transfer the spinach to a cutting board and roughly chop. Add to the vegetable mixture; stir until combined.

Combine ½ cup mozzarella, ricotta, ½ cup Parmesan, pesto, egg and the remaining ¼ teaspoon salt in a medium bowl; stir until well blended.

Spread 1 cup marinara in the prepared baking dish; top with a layer of 4 noodles. Spread 1 cup ricotta mixture evenly over the noodles; top with 2 cups vegetable mixture. Repeat the layers once. Top with the remaining 4 noodles, 1 cup ricotta mixture and 1 cup marinara. Sprinkle with the remaining 1½ cups mozzarella and ½ cup Parmesan. Cover with foil.

Bake for 30 minutes. Carefully remove the foil; bake until the top is browned around the edges, about 20 minutes more. Let cool slightly, about 10 minutes. Slice and serve topped with basil. Additional reporting by Carrie Myers, M.S. and Linda Frahm