Cook the pasta according to package instructions. Drain and set aside.
Sauté aromatics – Heat olive oil in a skillet over medium heat. Add sliced onions/shallots and cook until softened. Add minced garlic and cook until fragrant (about 30 seconds).
Brown the sausage – Add sliced al pastor sausage and cook until caramelized.
Heat the soup in a saucepan, thinning with milk or cream if needed.
Combine everything – Add the cooked pasta and sausage mixture to the sauce. Stir well to coat.
Finish with shredded cheese, salt, and pepper. Serve hot.