Fry the onion and garlic in a pan over medium heat for 5 minutes, stirring occasionally. Add the corned beef, break it up and fry for 5 minutes, stirring constantly. Add the tomatoes and simmer for 10 minutes.
Meanwhile, cook the spaghetti in salted water until al dente. Drain and add to the pan. Stir in the parsley and chilli flakes. Season to taste with salt and pepper. Mix well and heat for a few minutes.