Mix soy sauce, sesame oil, ginger, garlic, and lime juice in a bowl.
This is your flavorful marinade.
Place tuna steaks in a shallow dish or zip-lock bag.
Pour marinade over the tuna.
Cover and refrigerate for at least 30 minutes.
Heat a skillet over high heat.
Add tuna steaks to the hot skillet.
Sear for 1-2 minutes on each side, aiming for a rare center.
Sprinkle sesame seeds on the tuna steaks.
Press gently to adhere.
Sear for an additional 30 seconds on each side.
Remove tuna from the skillet.
Slice thinly.
Serve with a side of your choice.