Preheat oven to 375°F (190°C) and lightly grease a 9x13-inch baking dish with cooking spray or butter.

Heat olive oil in a large skillet over medium-high heat. Add the chopped onion and cook for about 4 minutes until softened and translucent.

Add minced garlic, zucchini, yellow squash, bell pepper, and mushrooms. Cook for 5-7 minutes, stirring occasionally, until vegetables are tender-crisp.

Add broccoli and spinach, cooking until broccoli is tender-crisp and spinach is wilted, about 2-3 minutes. Remove from heat.

In a medium bowl, combine ricotta cheese, drained cottage cheese, egg, Parmesan cheese, 1 cup mozzarella cheese, Italian seasoning, salt, and pepper. Mix thoroughly until completely combined and smooth.

Spread about 1 cup of marinara sauce evenly across the bottom of your prepared baking dish. Arrange a single layer of lasagna noodles over the sauce, breaking pieces to fit if needed.

Spread half of the cheese mixture over the noodles, followed by half of the cooked vegetables, half of the lentils, and about 1 cup of shredded mozzarella cheese.

Repeat the layering process: add another cup of sauce, noodles, remaining cheese mixture, remaining vegetables, remaining lentils, and 1 cup of mozzarella cheese.

Place the final layer of noodles over the top, spread the remaining marinara sauce evenly, and sprinkle with the last of the mozzarella cheese.

Cover the baking dish tightly with foil and bake for 30 minutes. Remove the foil and continue baking for 15-20 minutes until the cheese is bubbly and golden brown around the edges.

Let the lasagna stand for at least 10 minutes before cutting to allow the layers to set. Garnish with fresh chopped basil before serving.