The wide variety of mayonnaise in the shops is ever increasing. I think garlic mayonnaise goes particularly well with tuna but you could choose lemon, mustard or French.
Serves 1
1 hot baked potato
125g (4 oz) can of tuna in oil, drained
2 tablespoons garlic mayonnaise
half a red onion or 3 spring onions, chopped
salt and freshly ground black pepper
Method
Cut a large cross into the potato and squeeze the potato to open it out. Mix together the tuna, mayonnaise, onions and season to taste. Spoon the mixture inside the potato and sprinkle over a little black pepper