You will need;
- 4 x 150g fillets of any white fish (skinned and boned)
- 2 ripe tomatoes
- 100g cheddar cheese (white or yellow)
- 1 onion (finely chopped)
- 4 tablespoons of mayonnaise
- Knob of butter
- Salt and freshly-ground black pepper
- Vegetable oil (for greasing)
Cut the tomatoes in half and remove the seeds, then finely dice the flesh and place in a bowl. Finely dice the cheese and add to the bowl with the spring onions, then just bind with the mayonnaise. Season to taste.
Preheat the grill to high. Arrange the fish on a lightly oiled, sturdy baking sheet and season lightly, then grill for 4-6 minutes until almost tender. The timing will depend on the thickness of the fillet. To check that it is cooked, gently prod the thickest part of the fish with the point of a knife and the flakes should separate easily.
Quickly spread the mayonnaise mixture on top and flash under the grill for another 2 minutes or until the cheese is bubbling and golden.