3 Tbsp. rice vinegar
2 Tbsp.finely grated peeled fresh ginger
2 Tbsp. peanut oil
2 Tbsp. Asian sesame oil
2 Tbsp. soy sauce
1 Tbsp. chopped fresh parsley
1 serrano chile, seeded, minced
Pepper to season
1 1/2 pounds ahi tuna steaks about 1/2″ thick
Nonstick vegetable oil spray
Whisk first 7 ingredients in medium bowl to blend; season to taste with pepper. Transfer 3 tablespoons marinade to small bowl and reserve. Add tuna to remaining marinade in medium bowl and toss to coat. Refrigerate about 40 minutes.
Spray grill rack with nonstick spray. Prepare barbecue (medium-high heat). Grill steaks to desired doneness, turning frequently, about 4 minutes total for medium-rare. Transfer to platter. Drizzle reserved marinade over.