Remove with a slotted spoon to a large bowl and set aside.Reduce the heat to medium, add the onions, and season with salt and pepper. Cook, stirring occasionally, until the onions have softened and are just starting to brown, about 6 minutes. Turn off the heat.When the water is boiling, add the broccoli and cook until crisp-tender, about 3 minutes. Using the slotted spoon, transfer the broccoli to the bowl with the sausage.Return the water to a boil, add the pasta, and cook according to the package directions or until al dente. Reserve 1/2 cup of the pasta water, drain, and return the pasta to the pot; set aside.Return the pan of onions to medium heat, add the cream, and stir, scraping up any browned bits from the bottom of the pan. Bring to a simmer and cook until slightly thickened, about 2 to 3 minutes.