Full of flavor and hearty veggies, this truly is the Best Vegetarian Lasagna! Smothered in tender pasta, exquisite sauce and melty cheese this Lasagna is going to hit the spot! And I promise you won't miss the meat!
Preheat the oven to 375 degrees Fahrenheit and spray a 9 x 13 x 2 ½-inch baking dish with nonstick cooking spray and set aside.
Heat a large skillet over medium-high heat and add 1 tablespoon olive oil. Add 1 ½ cups diced zucchini, 4 ounces chopped mushrooms, 1 ½ cups diced carrots, and 1 cup diced onion and cook for 4-5 minutes until the vegetables are tender. Add 2 cups spinach and cook for an additional minute, until the spinach begins to wilt.
Add 1 (28-ounce) can crushed tomatoes, 2 (6.5-ounce) cans tomato sauce, 1 (6-ounce) can tomato paste, 2 tablespoons Italian seasoning, ¼ cup granulated sugar, and 1 tablespoon chopped fresh basil. Stir to combine and simmer over low heat for about 10 minutes, then season with salt and ground black pepper to taste.
Meanwhile, bring a large pot of water to a rolling boil over high heat. Add 12 lasagna noodles and cook for 8- minutes, until al dente. Drain and rinse in cold water.
Combine the 16 ounces ricotta cheese, ½ cup grated parmesan, and 1 large egg in a medium bowl.
Assemble the lasagna with 1 cup of the vegetable mixture on the bottom. Lay 1 single layer of noodles on top, followed by ½ cup of the cheese mixture and a handful of the 2 cups shredded mozzarella cheese. Repeat the layers until all of the ingredients are used up, ending with the remaining mozzarella on top.
Cover the baking dish with aluminum foil and bake for 20 minutes. Remove the foil and bake an additional 20-25 minutes or until the lasagna is heated throughout and the cheese on top is bubbly and browned. Let it cool for 10 minutes before serving.