For the Balsamic Reduction:
6 tablespoons balsamic vinegar
1 medium lemon, juiced
1 clove garlic, halved
For the Tuna:
1 1/2 teaspoons salt
1 teaspoon ground coriander
1 teaspoon paprika
1/4 teaspoon cayenne pepper
1 1/2 teaspoons coarsely ground black pepper
2 tablespoons vegetable oil
4 lemon wedges, for garnish
Make the balsamic reduction: Place the balsamic vinegar, lemon juice, and garlic in a small saucepan over medium-low heat.
Simmer until the mixture reduces by half. Turn off the heat and reserve until needed. This sauce does not have to be hot for serving. The reduction will thicken slightly as it cools.
In a small bowl, combine the salt, coriander, paprika, and cayenne pepper. Lay the tuna steaks out on a plate and sprinkle the spice mixture evenly on all sides.
Evenly coat the tuna steaks with the freshly ground black pepper and gently press it in so that it adheres to the surface, being careful not to smash the flesh.
Place a thick-bottomed frying pan or cast-iron skillet over medium-high heat. Add the oil and swirl to coat the pan. When you see small wisps of smoke, add the tuna to the pan and sear the steaks for about 1 minute per side or until the desired doneness is reached.
Remove the tuna steaks and place them on a cutting board. For presentation, cut each steak diagonally into 4 to 5 slices and fan on a plate. Serve with a small amount of sauce drizzled alongside. Garnish with a lemon wedge and enjoy.