Meanwhile, heat the oil in a large pan, then fry the onion over a medium-high heat for 5-6 mins, stirring occasionally, until golden and softened. Stir in the garlic and cook for a further 2-3 mins. Drain the peppers, reserving their juice, then stir into the onion. Cook for 2-3 mins to heat through. Blitz the mixture in a food processor, with 75ml/2½fl oz reserved juice from the peppers and 75ml/2½fl oz cooking liquid from the pasta, to make a chunky sauce.