Halve the tomatoes and scoop out the seeds. Roughly chop the flesh. Set aside.
Put 2 tablespoons of the olive oil in a shallow roasting tin with the spring onions, garlic and chilli. Place on the upper rack of the halogen oven.
Set the temperature to 225°C/437°F and cook for 2 minutes. Add the chopped tomatoes and a little salt and cook for a further 2 minutes.
Cook the pasta in a saucepan of salted boiling water for 2 minutes or until just tender. Drain well, return to the pan and stir in the tomato mixture. Tip into a shallow ovenproof dish and scatter with the prawns.
Brush the prawns with the remaining oil and place the tin on the lower rack of the halogen oven.
Set the temperature to 250°C (482°F) and cook for about 8 minutes until the prawns have turned pink and are just cooked through, turning them once halfway through cooking.