First prepare the ahi tuna. Remove the ahi from the tray/package. Lightly pat dry. Gently run the blade of knife across the surface of the ahi to clean the ahi. Do this on both sides of the ahi. Set aside.
Add a spoonful of neutral oil (I use avocado oil) to a frying pan. Turn it to medium-high heat. When the oil is hot, add the ahi.
Pan fry one side for 20 seconds. Flip it over and cook the bottom side 20 seconds.
Then turn the ahi onto the side and cook 20 seconds. Repeat for the other short side. You want all four sides to have a nice sear, but the inside to be raw.
Remove the ahi from heat and let cool. Then slice the ahi into ¼-inch slices. Make sure to slice against the grain.
Arrange the slice ahi on a plate, with the pieces slightly overlapping. Drizzle the ponzu sauce over the ahi. Top with chopped green onions and the roasted sesame seeds. Eat and enjoy ^_^