Preheat the oven to 200˚C, gas mark 6. Heat 1 tbsp oil in a large frying pan, add the onion and fry for 5 minutes. Add the garlic and fry for 3 minutes more.
Pour in the white wine and simmer for 2 minutes, then tip in the chopped tomatoes, oregano and caster sugar. Simmer for 6-8 minutes.
Tip into an ovenproof dish (about 1 litre in volume) and arrange the prawns on top. Scatter with the feta, drizzle with the remaining 1 tbsp oil and season.
Put in the oven, along with the ciabatta, and bake for 10 minutes, ensuring the prawns are fully cooked and pink throughout. Allow to cool for 5 minutes before serving the prawns with the bread to mop up the juices.