In a cast iron skillet heat the olive oil on medium heat. Then add the onion and sauté until it is translucent and slightly softened, stirring periodically.
Add the garlic and cook an additional minute, stirring often.
Add the broccoli, carrots, zucchini, and bell peppers to the pan and mix with the onion and garlic. Reduce heat to medium low and sauté until all the veggies are tender.
Meanwhile, bring a salted pot of water to a boil and add the pasta. Reduce to a simmer. Fresh pasta will only take 2-3 minutes to cook, but boxed pasta will take closer to 10 minutes.
When the pasta is tender, drain the cooking water and toss the noodles with olive oil to prevent sticking.
Add the marinara sauce into the veggie skillet and mix to combine. Continue cooking until the sauce is heated through. Salt and pepper to taste.
Serve the veggies and sauce over a bed of fettuccine and sprinkle with freshly grated Parmesan cheese if desired.