I have added wasabi, which is japanese horseradish, to these burgers because it gives them a wonderful kick. You wasabi in the asian sections of a supermarket, but if you can not get a hold of it a dab of english mustard will do.
Begin by making the salsa: Stir all the ingredients together and set aside at room temperature for at least an hour to let the flavours infuse.
Place the tuna in a food processor and pulse until coarsely minced. Transfer to a bowl and mix with the wasabi paste, sesame seeds and some salt and pepper. With damp hands, shaoe the mixture into 4 even sized burgers.
Preheat the oven to 200 degrees celcius. SPray a baking sheet with a little oil and arrange the burgers on the tray. Spray with a lttle more oil and bake for 15 minutes until golden brown and just cooked through.
Place the tuna burgers on the toasted ciabatta slices and top with a dalloop of salsa. Garnish with slices of fresh lime and serve warm.