Bring a large pot of salted water to a boil. Cook the ditalini pasta according to package instructions until al dente, about 8–10 minutes. Drain and set aside in a large bowl, reserving half a cup of pasta water.

In a skillet, heat 1 tablespoon of avocado oil over medium-high heat. Crumble in the sausage and sauté for 6–8 minutes until browned. Remove sausage with a slotted spoon, leaving rendered fat.

In the same skillet, add more avocado oil if needed, then add diced onion. Cook for 4–5 minutes until soft, then add minced garlic and sauté for 30 seconds.

Stir in the tomato paste and cook for 1–2 minutes to deepen flavor.

Pour in the chicken broth, scraping browned bits from the skillet. Simmer for 3–4 minutes.

Lower heat and stir in the heavy cream and Parmesan cheese until smooth and creamy.

Season with salt, pepper, and red pepper flakes. Fold in the cooked pasta and warm through for 1–2 minutes.