- Preheat the oven to 180°C.
- Peel the onions and roughly slice. In a hot frying pan, melt the butter and brown the onions, seasoning with sugar, salt and ground pepper.
- Place the slices of bread on a sheet of baking paper and spoon over a generous layer of onion confit, a few sardines, the tomatoes, halved, and two generous pieces of cheese.
- Bake in the oven for 5-6 minutes. When the cheese has nicely melted, serve hot with a green salad.
😉 Tip: You could replace the sardines in the recipe with mackerel fillets or anchovies.