In a sauté pan over medium heat, add olive oil. When hot, add sliced andouille sausage and onions and cook until sausage is browned on both sides, about 5 minutes.
Add diced tomatoes, chicken broth, garlic powder, salt, pepper, and tortellini. Stir to combine. Bring to a simmer, cover, and reduce heat to medium-low. Cook until pasta is al dente (check your pasta package's cooking directions for exact times). Most of the liquid should be absorbed in this step. If excess liquid remains in the pan, drain all but ¼ cup and return to the stovetop.
Remove lid and add heavy cream. Stir and cook until warmed through, about a minute.
Remove from heat. Add cheddar cheese, stir, and allow to rest for 5 minutes. Sauce will continue to thicken as it stands.
