Preheat oven to 350°F. Spray 9x13 baking dish with cooking spray.

In skillet heat the oil over medium low heat. Add the onions and cook until soft, about 5 mins. Stir in garlic and cook for 30 seconds.

Stir in beef and cook until browned, season with salt and pepper.

Stir in the tomato paste and then add teh tomatoes and mustard. Let teh mixture bubble gently until it is slightly thickened about 2 mins.

Toss meat mixture with pasta and spread into dish. Top with cheddar cheese and bake until the cheese is melted 15 mins.