Butterflied sardines with slow-roast tomato and strawberries

This is a lovely, warm summery starter or light lunch dish. I make it with mackerel fillets or with sardines – which, if you can get them, are generally cheaper. You can buy them ready prepared, opened out and backbones removed (‘butterflied’). The warm strawberry/tomato salad is good with feta too, maybe as part of a buffet. The combination of the sweet tomatoes and strawberries with the salty fish is surprising and delicious.