Preheat your oven to 375°F. If using regular lasagna noodles, bring a large pot of salted water to a boil and cook noodles according to package directions until just al dente, about 8–9 minutes. Drain, rinse with cold water, and lay flat on a lightly oiled baking sheet to prevent sticking. (Skip this step if using oven-ready noodles.)

Heat 2 tbsp olive oil of olive oil in a large skillet over medium-high heat. Add the 1 large yellow onion, diced 1 large yellow onion and cook until softened, about 4 minutes. Add the 4 cloves garlic and cook 1 minute more until fragrant. Add the 1 medium zucchini (diced into ½-inch pieces) 8 oz cremini mushrooms and 1 large yellow onion, diced 1 medium zucchini; cook, stirring occasionally, until the vegetables are tender and any liquid has evaporated, about 6–8 minutes. Stir in the 1 can tomato paste and cook for 1 minute. Pour in the 1 can crushed tomatoes, then add the 1 ½ tsp dried basil, 1 tsp Italian seasoning, ½ teaspoon 1 tsp salt, and ½ tsp black pepper. Stir to combine and simmer over medium-low heat for 10 minutes until the sauce thickens slightly. Taste and adjust seasoning.

While the sauce simmers, wilt the fresh fresh spinach roughly chopped in a dry skillet over medium heat (or microwave in batches) until fully wilted, about 2 minutes. Transfer to a colander and press out as much liquid as possible with the back of a spoon. In a mixing bowl, combine the 15 oz ricotta cheese whole milk preferred, beaten egg lightly, wilted 8 cups fresh spinach roughly chopped, 3 tbsp fresh parsley finely chopped (if using), and the remaining ½ teaspoon of salt. Stir until evenly mixed.

Spread about ¾ cup of the vegetable sauce across the bottom of a 9×13-inch baking dish. Lay 3–4 noodles in a single layer over the sauce. Spread one-third of the ricotta cheese whole milk preferred mixture over the noodles, then spoon 1 can tomato paste on top. Sprinkle with about ¾ cup of shredded mozzarella cheese and ½ cup grated Parmesan cheese of grated Parmesan cheese. Repeat the layers (noodles, ricotta, sauce, mozzarella, Parmesan) two more times. Finish with a final layer of noodles, the last of the sauce, and the remaining shredded mozzarella cheese and ½ cup grated Parmesan cheese on top.

Cover the baking dish tightly with aluminum foil (tent it slightly so it doesn't touch the cheese) and bake at 375°F for 30 minutes. Remove the foil and bake for an additional 20–25 minutes until the cheese is golden and bubbling and the edges are lightly caramelized. Remove from the oven and let the lasagna rest for at least 15 minutes before slicing and serving.