This crowd-pleasing pasta is packed with flavor and veggies. It's even got roasted red peppers hidden inside the easy tomato-based pesto sauce. Meatless sausage keeps it vegetarian while increasing the protein and adding flavor and texture.
Bring a large pot of salted water to a boil. Cook the pasta according to the package directions for al dente. Reserve 2 cups of the pasta cooking water before draining. Return the cooked pasta to the pot.
While the pasta cooks, heat the oil in a large nonstick skillet over medium-high heat. Add the onions, 1/2 teaspoon salt and a few grinds of black pepper and cook, stirring occasionally, until the onion just begins to soften, 3 to 4 minutes. Add the sausage, 1/4 teaspoon salt and a few grinds of black pepper and cook, stirring occasionally, until starting to turn golden brown, 4 to 5 minutes.
Meanwhile, combine the sun-dried tomatoes and the oil from the jar, red peppers, red pepper liquid, walnuts, parsley, Parmesan, vinegar, tomato paste, 1 teaspoon salt and a few grinds of black pepper in a food processor and process until smooth.
Add the sausage mixture and sun-dried tomato pesto to the pot with the pasta and stir until well combined, stirring in as much of the reserved pasta water as necessary to make a creamy sauce. Garnish with chopped parsley and more Parmesan.