To make Tuna Fish Cakes, start by draining the canned tuna.
While the rice is cooking, prepare the eel by grilling or frying it.
Put the tomato paste, olives, and butter into a blender or food processor and whizz until smooth.
Put the oats in the blender or food processor, slightly broken up.
Coat the fillets with the butter mixture while grilling.
Heat a large skillet over medium-high heat and add the fish cakes.
Serving Suggestions: To serve each burger, scoop a tablespoon of the relish, followed by a dollop of yoghurt sauce on top of a salmon patty. Top with cos lettuce leaves and garnish with a little grated carrot, red onion, mint and a lemon wedge.