1. Spread sesame seeds in shallow baking dish or pie plate and pat tuna steaks dry with paper towel.
2. Use 1 tbsp. oil to rub both sides of steaks and sprinkle with salt and pepper.
3. Press both sides of each steak in sesame seeds to coat.
4. Heat remaining 1 tbsp. oil in 12-inch nonstick skillet over high heat until just beginning to smoke; swirl to coat pan.
3. Add tuna steaks and cook 30 seconds without moving steaks. Reduce heat to medium-high; continue to cook until seeds are golden brown, about 1 1/2 minutes.
3. Using tongs, carefully flip tuna steaks; cook, without moving steaks, until golden brown on second side, about 1 1/2 minutes for rare or 3 minutes for medium-rare.
4. Make sauce by combining all ingredients; stirring until sugar is dissolved.
5. To serve cut into 1/2 inch-thick slices and service with ginger-soy sauce.