3 ½ cups homemade (or store-bought) tomato sauce
8 ounces no-boil lasagna noodles (or the ones you need to boil, and then just follow instructions on the box)
15 ounces ricotta cheese
3 cups chopped mixed vegetables (e.g., zucchini, broccoli, cauliflower, carrots, eggplant, mushrooms, etc), lightly steamed or sautéed
8 ounces grated mozzarella cheese
Preheat the oven to 350°F.
In a 9 x 13-inch rectangular pan, spread a thin layer of tomato sauce. Cover with one layer of noodles.
In a medium bowl, combine the ricotta with ¼ cup water to thin it out slightly. Use a spatula to spread ⅓ of this mixture over the noodles. Spread ⅓ of the tomato sauce over the ricotta, followed by ⅓ of the steamed vegetables. Sprinkle ⅓ of the mozzarella evenly over the vegetables. Repeat this layering two more times, starting with the noodles and ending with the mozzarella.
Cover with foil and bake until the noodles are tender, 35 to 40 minutes. Remove the foil and bake until the cheese starts to lightly brown, about 5 additional minutes. Remove from the oven and allow to rest for 5 minutes before cutting and serving.