To peel the tomatoes, score a cross in the base of each tomato. Put in a heatproof bowl and cover with boiling water. Leave for 30 seconds, then transfer to cold water and peel the skin away from the cross. Cut the tomatoes in half horizontally and scoop out the seeds with ateaspoon. Roughly chop the flesh.
Heat the oil in a large saucepan over medium heat, add the onion and cook for 3 minutes, or until soft. Add the tomato and cook, stirring occasionally, for 5 minutes, or until very soft. Stir in the stock, bring to the boil, reduce the heat and simmer for 10 minutes.
Cool slightly, then transfer to a food processor or blender. Process in batches until smooth, then return to the pan. Add the tomato paste and sugar and bring to the boil, stirring. Reduce the heat and stir in the cream. Season and serve with a swirl of cream and alittle parsley.