Start by bringing a large pot of salted water to a rolling boil. Add the penne pasta and cook according to package directions until al dente, about 10-12 minutes. Reserve ½ cup of pasta water before draining.

While the pasta cooks, heat a deep skillet over medium-high heat and pour in olive oil until it shimmers.

Add sliced red onion and carrot to the skillet, stirring for about 2 minutes until onions are translucent and carrots start to soften.

Toss in chopped broccoli and bell pepper, sautéing for another 2 minutes until they retain some crunch.

Introduce sliced squash and zucchini, cooking for 2-3 minutes until they start to soften.

Stir in minced garlic, diced tomatoes, and Italian seasoning, cooking for about 2 minutes until fragrant.

Transfer the vegetable mixture to the drained pasta pot or a large serving bowl and combine with the drained penne pasta.

Drizzle lemon juice and adjust seasoning with salt. Gradually add reserved pasta water until desired sauce consistency is reached.

Fold in grated Parmesan cheese and chopped fresh parsley. Serve immediately.