Bring a large pot of generously salted water to a boil. Add the penne and cook until 1 minute shy of al dente according to package directions. Reserve 1/4 cup of the pasta cooking water, then drain the pasta and set it aside.

While the pasta cooks, heat 2 tablespoons of the butter and the olive oil in a large skillet over medium heat. Add the diced onion and cook until softened, about 2 minutes.

Stir in the carrot and cook for 1 minute. Add the broccoli and bell pepper, cooking for another minute. Then add the asparagus (or zucchini) and minced garlic. If the pan looks dry, add the remaining tablespoon of butter just before adding the asparagus. Season the vegetables with salt and pepper, then transfer them to a plate and set aside.

To the now-empty skillet, add the remaining 1 tablespoon of butter, the chicken broth, Meyer lemon juice, and the reserved pasta water. Bring to a boil, scraping up any browned bits from the bottom of the pan. Let it simmer for 2 to 3 minutes.

Add the cooked pasta to the skillet and toss to coat. Continue simmering for 3 to 4 minutes, stirring occasionally, until the sauce reduces by half and clings to the noodles.

Return the sautéed vegetables to the skillet and toss everything together. Taste and adjust seasoning with salt and pepper. Sprinkle with freshly grated Parmesan and minced parsley. Serve immediately with extra Parmesan and lemon wedges on the side, if desired.