Cook the tortellini according to the package instructions. (Tip: Make sure not to overcook the tortellini; they should be al dente for the best texture.)
In a large skillet over medium heat, melt the butter and olive oil together. Add the diced bell peppers, onion, and garlic. Cook until softened, about 3 minutes. (Tip: Stir occasionally to prevent garlic from burning.)
Then, add the sliced andouille sausage to the skillet. Cook for an additional 5 minutes, allowing the sausage to brown slightly for added flavor.
Reduce the heat to low. Add the Cajun seasoning, heavy cream, and sour cream. Stir until the sour cream is well mixed into the sauce.
Mix in the Parmesan cheese until melted and creamy. (Tip: For a creamier sauce, you can add a splash more of heavy cream.)
Add the cooked tortellini to the skillet and toss everything together to coat well with the sauce.
Notes
For an extra kick, sprinkle some red pepper flakes on top before serving.