Heat the oil in a pan and fry the onion for about 5 mins until softened
Add the garlic, chopped tomatoes, tomato purée, sweet paprika, chilli powder, sugar and a pinch of salt, then bring to the boil, stirring occasionally
Lower to a simmer and cook for 10 mins until pulpy
Can be kept chilled for up to 24 hrs
Heat oven to 200C/180C fan/gas 6
Pat the potatoes dry with kitchen paper, then tip into a roasting tin and toss in the olive oil and some seasoning
Roast for 40-50 mins until crisp and golden
Tip the potatoes into serving dishes and spoon over the tomato sauce
Sprinkle with some fresh parsley to serve