Heat a pan over medium-high heat. Drizzle tuna with olive oil on both sides, and season with salt and pepper.
Sear the tuna for 2 minutes on each side. Remove and rest.
Make the mayo: mix the mayonnaise, miso, ginger and honey in a bowl.
Toast the burger buns, then spread with the mayo, add a slice of tomato and a lettuce leaf, then the tuna, then top with more lettuce. Enjoy!