1. Spoon 1 tablespoon soy sauce over fish; let stand 5 minutes.
2. Combine the remaining 1 tablespoon soy sauce, ginger marmalade, and 2 teaspoons wasabi paste in a small bowl, stirring with a whisk.
3. Heat a grill pan over medium-high heat. Coat pan with cooking spray. Add fish to pan; cook 2 minutes on each side. Spoon marmalade mixture over tuna; cook 1 minute or until medium-rare or until desired degree of doneness. Remove tuna from pan; sprinkle with cilantro.