4 c. low-sodium vegetable broth
8 oz. linguine, uncooked
1 small onion, halved and sliced thin
1 lb broccoli crowns, cut into large florets (about 2 cups)
1.5 lbs asparagus, ends snapped off and cut into 2-inch pieces
4 oz. sliced white button mushrooms (about 1 cup)
4 large cloves garlic, minced
1/4 tsp crushed red pepper flakes
1 tsp kosher salt
1/2 tsp freshly ground black pepper
2 tbsp olive oil
3/4 c. frozen peas
1 small handful fresh parsley, chopped (about 1/2 cup)
1/4 c. heavy whipping cream
2 tbsp grated Parmesan cheese
2 tsp freshly grated lemon zest
Additional salt and pepper to taste
Additional Parmesan cheese for serving, if desired