Step 1: Prepare the Tuna - Pat the ahi tuna steak completely dry using paper towels. This helps create a proper sear and prevents excess moisture from steaming the fish.
Step 2: Season the Steak - Sprinkle sea salt and cracked black pepper evenly over both sides of the tuna. Press the toasted sesame seeds firmly onto all sides so they adhere well to the surface.
Step 3: Heat the Skillet - Place a cast-iron skillet over high heat until extremely hot. Add the vegetable oil and swirl it around the pan. The oil should shimmer immediately.
Step 4: Sear the Tuna - Carefully place the tuna steak into the skillet. Sear the first side for about 1 to 1½ minutes until lightly crisp. Flip gently and cook the second side for another minute. The exterior should look beautifully seared while the center remains medium-rare.
Step 5: Rest Before Slicing - Transfer the tuna to a cutting board and let it rest for about 1 minute. This helps the juices settle while keeping the fish tender.
Step 6: Slice and Serve - Using a sharp knife, slice the tuna into thin strips against the grain. Arrange over white rice with grilled broccolini and radish for a restaurant-style presentation. Serve with ponzu sauce, sweet chili sauce, wasabi, and fresh ginger on the side.
