Cook the pasta according to package directions. Reserve 1 cup of the cooking liquid before draining.

While the pasta is cooking, heat the oil in a saute pan over medium heat. Add the onions and saute until soft, about 3 minutes. Add the garlic, carrots, broccoli, and peas and saute another 3-5 minutes. Add the spinach and cook for 1 minute more.

Add the vegetables to the cooked pasta, toss with the lemon juice, parmesan cheese and reserved pasta water to combine thoroughly.