Cook tortellini according to package directions; drain and set aside.
Meanwhile, heat the oil in a large saucepan with a tight-fitting lid over medium heat; add garlic and black walnuts; stir-fry until garlic begins to brown and soften. Add tomatoes (with their juices), basil, oregano and parsley.
Bring to a boil then reduce heat, cover and simmer for 5 to 7 minutes. Add cooked tortellini to the tomato sauce; season with salt, pepper and cayenne pepper.
Sprinkle with cheese and serve.