Set up your grill so it's nice and hot, the tuna prep will only take about 20 minutes. It doesn't hurt to grease your grates so the tuna doesn't stick as much. I just dip a rag in some vegetable oil and rub it onto the grates.
In a mixing bowl, mix together your salt, pepper, and olive oil. Then put in your tuna steaks, coat them so the salt and pepper coat the steak evenly. Let the tuna rest for about 10 to 15 minutes, this will let the steaks get to room temperature. By doing so, this will allow your steak to cook evenly and will allow moisture to spread normally through the steak.
Once the grill is hot, place your tuna steaks on the grill. This is where it gets tricky (and some people prefer their tuna steak to be cooked more, I tend to think rare is the best way to eat your tuna, but that's up to you) Once the tuna begins to turn a tannish beige color, flip the tuna onto its other side. Once that side turns the same color, take it off the grill. The steak should be tan all around but pink in the middle.
I like to serve the tuna with a little mayo based sauce. To make this just mix the mayo, lemon juice and paprika. This will give the tuna a little more flavor.
Serve with a Shirazi Salad and enjoy!