Lightly oil 2 (8 ounce) fresh tuna steaks with vegetable oil. Stir 2 tbsp soy sauce, 2 tbsp seasoned rice vinegar, 1 tbsp finely grated raw horseradish root, 4 cherry tomatoes sliced, and 1/2 tsp hot chile paste in a bowl until well combined. Let sit for 20 minutes. Place steaks over hottest part of the grill and cook for 3 minutes per side. Transfer to a plate. Spoon soy sauce mixture over steaks and garnish with1 tbsp minced green onion.