Heat the oil in a large saucepan over a medium heat, add the onion and celery and cook until soft.
Meanwhile, score a cross in the base of each tomato, then put in a heatproof bowl of boiling water for 1 minute. Plunge into cold water, then peel the skin away from the cross. Halve the tomatoes, then scoop out the seeds and discard. Roughly chop the flesh.
Add the tomatoes, stock, onions and celery to the pan and bring to the boil. Add the pasta and cook for 10 minutes or until al dente. Season to taste with salt and pepper and stir in the parsley.
Remove from the heat, ladle into warmed bowls and drizzle with oil before serving.