Preheat oven to 200C/180C fan forced. Cook the pasta in a large saucepan of salted boiling water following packet directions or until al dente. Drain.
Meanwhile, heat the oil in a large saucepan over medium-high heat. Add the onion and capsicum. Cook, stirring, for 5 minutes or until softened. Add the beef. Cook, stirring with a wooden spoon to break up any lumps, for 5 minutes or until browned.
Add the taco seasoning to the pan. Cook, stirring, for 1 minute or until well combined. Add the pasta, salsa and cheese sauce. Season. Cook, stirring, until combined and warmed through. Transfer to a baking dish and smooth the surface. Scatter with cheese. Bake for 20-25 minutes or until golden.
Serve topped with sour cream, tomato, avocado and shallot.
