Bring a large pot of salted water to a boil. Add the pasta and cook according to the package directions, adding the asparagus during the last 2 minutes. Drain the pasta and asparagus.
Meanwhile, melt the butter in a large Dutch oven over medium heat. Add the sausage and cook, breaking it up with a wooden spoon, until browned, about 5 minutes.
Add the garlic, salt, black pepper, and red pepper flakes to the sausage and cook, stirring, until fragrant, about 1 minute. Add the chicken broth and cook 1 minute, scraping up the bottom of the pot. Reduce the heat to medium-low and stir in the heavy cream. Simmer until thickened, 3 to 4 minutes. Reduce the heat to low and stir in the parmesan, lemon zest, and lemon juice.
Add the pasta, asparagus, and basil to the pot and stir to coat. Serve with parmesan for topping.
