Mix the marinade ingredients together except the vegetable oil. Coat the tuna on all sides. Cover and refrigerate for at least 1 hour.
Heat a non-stick pan or cast iron skillet over medium high heat. Add vegetable oil and sear the tuna about 2 minutes on each side or longer if you like well done.
Serve with rice if desired.
Recipe by The Gluten Free at https://www.theglutenfree.com/pan-seared-tuna-with-ginger-sauce/