Spray a pan with low calorie cooking spray.
Sauté the bacon and onions over a medium heat for 10-15 minutes, until the bacon crisps and the onions soften and caramelise.
Stir in the chilli flakes and tomato puree and cook for 30 seconds.
Add the tomatoes and Worcestershire sauce, stir and increase the heat until the sauce bubbles.
Reduce the heat and allow to gently simmer for 15 minutes.
Meanwhile, bring a pan of salted water to the boil and cook the spaghetti according to packet instructions, usually between 9-12 minutes.
When cooked, drain the spaghetti and add to the pan of sauce. Stir to coat the spaghetti well.
Divide into 4 pasta bowls and top with a sprinkling of grated Pecorino and some freshly ground black pepper.