Take your tuna, and pat it dry
Dump your toasted sesame seeds onto a plate, and press the tuna piece into it to coat the exterior, flip over and do it to the other side
Heat olive oil in a saute pan, and when hot, sear ahi on both sides in pan (2-3 minutes per side) middle should be pink still
Mix salsa ingredients together, squeezing lime juice over the top.
Serve ahi over a bed of spinach, topped with mango salsa