Heat a large deep skillet over medium-high heat. Add the sausage, break it up, and cook until browned and cooked through, 6 to 8 minutes. Transfer to a plate, leaving the fat in the pan.

Reduce heat to medium. Add the onion and cook until soft, about 4 minutes. Stir in the garlic and sun-dried tomatoes, cooking 1 minute.

Pour in the broth and cream, scraping up browned bits. Bring to a boil, add the penne and a pinch of salt. Reduce heat to medium-low, cover, and simmer for 12 to 14 minutes, stirring occasionally, until pasta is tender and sauce thickens.

Remove from heat. Stir in the spinach and cooked sausage, then the Parmesan, until spinach is wilted and cheese is melted. Season with salt and pepper. Serve immediately.