Cut the garlic and onions. Fry in a pan in a little heated oil until golden brown. Then add the diced pepper and the shredded tuna. Let everything stew for about 5 minutes. Then season the filling with salt and pepper.
Take a square piece of puff pastry, add some of the filling (approx. 1-2 tablespoon) and close the dough in a triangle shape. Press the edges together firmly with a fork.