Start by preheating your grill on high.
As the grill warms up, take your tuna steaks and drizzle them with a tablespoon of olive oil. Season both sides with salt and pepper.
Now, for the Lemon Relish: in a bowl, combine lemon juice, zest, the remaining olive oil, chopped parsley, minced garlic, and red chili flakes. Stir well.
Grill your tuna steaks for about 2-3 minutes on each side or until your desired doneness is achieved. The outside should be slightly charred with a pink center.
Once off the grill, let the tuna rest for a minute or two.
Serve the tuna steaks hot and spoon the Lemon Relish over them generously.