1. Add the cubed tuna to skewers, and season with salt and pepper on both sides.
2. Grill the tuna in a grill pan or on a grill for two to four minutes on each side, to preferred doneness.
3. Meanwhile, chop all of the gremolata ingredients using a sharp knife or food processor. Set aside.
4. Heat up a wide pan over high heat. Add in the tomatoes, garlic, olive oil, salt and pepper. Cook covered for 10 minutes until the tomatoes start to burst, stirring occasionally.
5. Once the tuna is cooked, top with the gremolata and serve with cooked tomatoes.