Tuna: Whisk together the olive oil, lime juice and garlic in a bowl. Rub the tuna steaks with the mixture. Place the steaks in a sealable container and marinate/chill in refrigerator 3 hours.
Salsa: Combine the mango, capsicum, Spanish onion, shallots, coriander and jalapeno in a bowl then stir. Add the lime juice and 1 1/2 teaspoons olive oil and toss to combine. Chill in refrigerator 1 hour.
Spice Rub: Stir together the paprika, cayenne pepper, onion powder, salt, pepper, thyme, basil, oregano and garlic powder in a bowl.
To Prepare: Remove the tuna steaks from the refrigerator and gently rinse with water and then dip each side of each steak in the spice mixture to coat.
Heat 2 tablespoons olive oil in a large frypan over medium heat or preheat oil on a barbecue plate to medium. Gently lay the tuna steaks into the hot oil. Cook the tuna on one side for 3 minutes; remove to a plate. Pour the remaining 2 tablespoons olive oil into the frypan/plate and let it get hot. Lay the tuna with the uncooked side down and cook another 3 minutes; remove from heat immediately.
Spoon about 1/2 cup of the mango salsa onto each of 4 plates. Place the tuna steaks on top of the salsa and serve immediately.