Fish in a flash

8 cherry tomatoes, halved

1 small red onion, chopped

½ tsp red chilli flakes

1cm/½ inch piece ginger, peeled and grated

2 garlic cloves, peeled and bruised

2 tbsp olive oil

1 x 300g/10½oz fillet of white fish (haddock, pollack or salmon)

juice of 1 lemon

1 tsp balsamic vinegar

salt

freshly ground black pepper