In a small bowl, whisk together soy sauce, minced ginger, sesame oil, garlic powder, and honey. Set aside.
Pat the tuna steaks dry with paper towels. Season lightly with salt and pepper.
Heat a non-stick skillet over medium-high heat. Add the tuna steaks and sear for 1-2 minutes per side, until browned but still rare in the center.
Remove the tuna from the skillet and set aside.
In the same skillet, add the prepared soy ginger sauce and water. Bring to a simmer.
In a small bowl, whisk the cornstarch with 2 tablespoons of water until smooth. Pour the cornstarch slurry into the simmering sauce and whisk until thickened.
Return the tuna steaks to the skillet and spoon the sauce over them. Cook for another minute until heated through.
Serve the soy ginger tuna immediately, garnished with sesame seeds and sliced green onions.
Notes
This recipe is versatile. You can serve it with rice, noodles, or a fresh salad.