Heat your grill to high. Make the "Barbecue" Rub by combining all the ingredients in a bowl. Brush each mahimahi fillet on both sides with the oil. Rub 1 side of each fillet with 1 tablespoon of the "Barbecue" Rub and grill, rubbed side down, until slightly charred and a crust has formed, 2 to 3 minutes. Turn the fish and grill for 3 to 4 minutes longer, or until cooked to medium doneness. Top each fillet with a few tablespoons of the pesto and garnish with cilantro leaves.