Boil salted water in a large pot. Add penne pasta and cook according to package instructions until al dente, about 8-10 minutes. Reserve 1/2 cup of pasta water, then drain.

Heat olive oil in a large skillet over medium-high heat until shimmering, about 1 minute.

Sauté chopped red onion and carrots in the skillet, stirring for about 2 minutes until onion is translucent.

Add broccoli florets and diced bell pepper, sauté for an additional 2 minutes until broccoli is tender-crisp.

Incorporate sliced squash (zucchini) into the skillet, stirring for another 2-3 minutes until soft yet firm.

Add minced garlic and halved tomatoes with Italian seasoning, cooking for about 2 minutes until fragrant.

Combine the drained pasta with the sautéed vegetables, tossing well to mix.

Drizzle in fresh lemon juice and adjust seasoning with salt. Use reserved pasta water for sauce consistency.

Fold in grated Parmesan cheese and chopped parsley, allowing the cheese to melt into the warm pasta.

Serve immediately, garnishing with extra parsley if desired.