Boil salted water in a small pot and cook pasta according to package directions. Reserve 1/2 cup of pasta water.
Meanwhile, heat olive oil over medium-high heat in a large skillet with deep sides.
Add the sliced mushrooms evenly to the pan and fry without stirring for 3 minutes. Stir and let sit an additional 3 minutes without disturbing.
Stir mushrooms and add zucchini, onion, garlic, salt and pepper, and Italian seasoning. Cook until the zucchini and onion just begin to soften, approximately 3-4 minutes.
Add bell pepper, stirring to incorporate with other ingredients and cook 3 minutes.
Add tomato, spinach, butter, lemon zest, lemon juice, basil, crushed red peppers (if using), a pinch more of salt and pepper, parmesan, and reserved pasta water. Stir until the spinach wilts and the butter sauce emulsifies together. Remove from heat.
Add the pasta to the sauce and veggie mixture, mixing thoroughly to ensure all pasta is coated in the sauce and the veggies are evenly distributed.
Serve topped with additional parmesan cheese.