Not all of us are sushi fans, but if you like raw ahi tuna, sashimi style, this delicious preparation might be a nice change of pace. The trick is to dice the tuna very finely, which takes a bit of patience but creates a wonderful presentation. The drizzle of infused tangerine or orange oil adds a dramatic visual impact (especially if you serve the tartare on a white plate), while the bright citrus notes of the oil are the perfect counterpoint to the mellow tuna. If flavored oils aren't available in your area, or you'd like to make your own, try our recipe for Tangerine Oil. The tartare can be prepared up to 2 hours in advance of serving and the plates garnished with tangerine oil, sea salt, and herbs at serving time.
Slice the tuna into very thin slices, about 1/8-inch thick. Cut each slice into 1/8-inch thick strips, and then cut these into a tiny dice. The resulting cubes of tuna should each be about 1/8 of an inch. Working with very cold tuna will help in the dicing process, so keep the portion you're not slicing on ice or in the refrigerator while you work.
Place the tuna in a small bowl and add the cucumber, olive oil, lime zest and juice, jalapeno, and mint. Stir gently to combine. Divide the tartare among 4 chilled plates and drizzle the citrus oil, if using, around the perimeter of the plates. Sprinkle the tartare with sea salt and garnish with mint sprigs. Serve immediately.