In a large pot, bring salted water to a rolling boil. Add penne pasta and cook according to package instructions until al dente, usually about 8–10 minutes. Before draining, reserve ½ cup of pasta water. Drain the pasta and set it aside, keeping it warm.

In a deep skillet, heat 2 tablespoons of olive oil over medium-high heat. Allow the oil to shimmer.

Add the chopped red onion and sliced carrots to the skillet, stirring gently. Sauté for about 2 minutes.

Next, toss in the broccoli florets and diced bell pepper. Sauté for another 2 minutes.

Add the sliced squash and zucchini to the skillet, continuing to sauté for an additional 2-3 minutes.

Stir in minced garlic, diced tomatoes, and Italian seasoning, sautéing for another 2 minutes.

In a large bowl, combine the sautéed vegetables with the drained penne pasta. Toss together gently.

Drizzle with fresh lemon juice, then season with salt and mix while adding reserved pasta water until you reach desired creaminess.

Toss in grated Parmesan and chopped fresh parsley, mixing until well combined. Serve immediately.