In a mixing bowl combine the mince, breadcrumbs, minced onion, cayenne and seasoning. Mix well using your hands.
Use a burger press to make 4 thin burgers or use your hands. If you have time, chill in the fridge for a little while to firm up.
Heat a frying pan with a little oil. Add the burgers and to one side of the pan add the sliced onion. Cook over medium to low heat for approximately 12 minutes or until the burgers and onions are cooked.
Lightly toast the ciabatta rolls. Serve the burgers in a roll (2 per roll as these rolls are long or double up in a burger roll). Top with cheese, fried onions and sweet chilli sauce.