9oven-ready (no boil) whole wheat lasagna noodles(I like Delallo), about 5.5 ounces
Fresh basilfor serving
Preheat the oven to 400 degrees F. Coat a 9x13-inch baking dish with nonstick spray.
In a large saucepan or Dutch oven, heat the olive oil over medium heat. Add the sweet potato, bell peppers, red onion, zucchini, dried basil, and ¼ teaspoon kosher salt. Cook until the vegetables are tender and begin to brown, about 10 minutes.
Add the tomato sauce and balsamic to the vegetables. Stir to combine then bring the mixture to a gentle simmer. Let simmer, stirring occasionally, for 10 minutes.
In a large bowl add the ricotta, 1/4 cup Parmesan, egg, and remaining 1/2 teaspoon salt. Mix well, until the mixture is evenly combined.
Stir in the spinach, using a fork to break it up and distribute it as evenly with the ricotta mixture as possible.
Spread a thin layer of the vegetable tomato sauce on the bottom of the prepared baking dish in an even layer. Arrange 3 lasagna noodles on top, breaking the ends if needed so that they fit. Leave some space around the noodles, as they will expand as they cook.
Top the noodles with 1/3 of the remaining sauce, half of the ricotta mixture, the next 1/3 portion of the sauce, and 1/2 cup of the mozzarella.
Top with 3 more noodles, the remaining ricotta mixture, and 1/2 cup mozzarella (no tomato sauce in this layer).
Top the cheese with the 3 final noodles. Spread the remaining sauce over the top.
Sprinkle with the remaining 1 cup mozzarella cheese and remaining 1/4 cup Parmesan.
Cover the lasagna with foil (be careful not to let the foil touch the top of the cheese or it will stick—I like to stick a few toothpicks in the top of the lasagna so that they are poking up and keep the foil off of the cheese). Bake it covered for 25 minutes.
Remove from the oven, uncover, and rotate the pan by 180. Continue cooking uncovered for 15 to 20 more minutes, until it is hot and bubbly and the cheese is beginning to have brown spots.
Remove from the oven and let cool for 15 minutes to set. Sprinkle with fresh basil, then slice and serve.
TO STORE: Refrigerate lasagna in an airtight storage container for up to 4 days.
TO REHEAT: Rewarm leftovers in a baking dish in the oven at 350 degrees F.
TO FREEZE: Freeze leftovers in an airtight freezer-safe storage container for up to 3 months. Let thaw overnight in the refrigerator before reheating.
TO MAKE AHEAD: Prepare the lasagna as directed, then cover and refrigerate it for up to 1 day or freeze for up to 3 months (make sure your dish is freezer-safe). If refrigerated, let the lasagna come to room temperature prior to baking. If frozen, let the lasagna thaw overnight in the refrigerator before bringing it to room temperature and baking.