Preheat oven to 220°C, gas mark 7. In a medium bowl, combine the crab meat, salad onions, lime zest, ½ tbsp of soy sauce and flour with the egg yolk.
Place the breadcrumbs on a lipped plate. Line a medium baking tray with a sheet of Bacofoil (non-shiny side up, to prevent sticking).
Scoop up a heaped tablespoon of the crab mixture, then pat down into a disc shape and dip in the breadcrumbs to coat on both sides. Repeat with the remaining mixture to make 8, placing onto the foil-lined tray. Bake the crab cakes for 20 minutes, turning halfway through, until crisp and golden.
Meanwhile, mix the mayonnaise, remaining soy sauce and juice of half the lime together to make a dip. Drizzle the remaining lime juice over the fishcakes and scatter over the red chilli and salad onion. Serve with the dip on the side.