Bring a large pot of salted water to a rolling boil. Add the penne pasta and cook according to package instructions, typically 8-10 minutes, until al dente. Reserve 1/2 cup of pasta water, then drain.

In a large skillet, heat olive oil over medium-high heat. Add chopped red onion and sliced carrot, sauté for about 2 minutes until translucent.

Add broccoli florets and sliced bell pepper to the skillet. Sauté for another 2 minutes until softened yet vibrant.

Introduce the sliced zucchini and squash, sauté for 2-3 minutes until nearly tender.

Stir in minced garlic, halved tomatoes, and Italian seasoning. Cook for another 2 minutes until garlic is fragrant.

Combine sautéed vegetables with drained pasta in a pot or large bowl. Drizzle lemon juice and mix, adding reserved pasta water for desired consistency.

Toss in grated Parmesan cheese and chopped parsley, mixing thoroughly. Serve immediately.