Combine all marinade ingredients in a bowl. Add the tuna cubes and allow to marinate for 1 hour.
Thread the tuna onto skewers (if they are wooden they will need to be soaked in advance). Heat a large frying pan or grill plate over medium heat and spray with olive oil. Cook the tuna for one minute on each side. It should remain rare.
Combine all the salad ingredients in a large bowl. Serve with the tuna