Makes 4 appetizer servings
For the tuna
1 teaspoon kosher salt
1 teaspoon crushed cumin seed
1 teaspoon crushed fennel seed
1/4 teaspoon red-chili flakes
1 teaspoon coarsely ground or cracked black pepper
1/2-pound chunk of sashimi-quality tuna, cut into 3 by 3-inch portions [we did not cut the tuna into portions until after it was cooked]
Few drops of vegetable oil
In a small bowl, combine the salt, cumin seed, fennel seed, chili flakes, and pepper. Coat the tuna well on each side with the mixture.
Heat a skillet or sauté pan over high heat until very hot. Heat the oil until it is smoking and sear the tuna 15 seconds on each side.
Place the tuna on a plate and refrigerate until firm, about 10 minutes or up to 3 hours [we ate the tuna hot from the pan].
For the marinated cucumber
1/2 cup champagne vinegar
3 to 4 tablespoons sugar
1 long, thin, seedless cucumber, peeled, sliced very thin lengthwise on a mandoline or with a sharp knife
In a small saucepan over low heat, combine the vinegar and sugar and heat gently, stirring occasionally, until the sugar is dissolved. Remove from the heat and allow to cool to room temperature. Pour the cooled mixture over the cucumber slices and marinate at room temperature for 30 minutes. Drain the cucumber and reserve.
Red Chili Vinaigrette
Makes 1 cup
1/4 cup champagne vinegar
3/4 cup red-chili oil
Kosher salt and freshly ground black pepper
Pinch of red-chili flakes
Place the vinegar in a small bowl and drizzle in the chili oil, whisking until incorporated. Add the salt, pepper, and chili flakes, and blend well.
To serve
Slice each piece of tuna about 1/8 inch thick, using a very sharp knife or an electric knife. [We did not slice the fish.] Make mounds of cucumber slices on 4 chilled plates and surround them with 3 or 4 slices of tuna. Drizzle the red-chili vinaigrette around the tuna.