Makes 4 servings. Difficulty
For sauce: 2/3 cup sour cream 1 Tablespoon water 4 teaspoons fresh lemon juice 1/4 cup chives, finely chopped 1 shallot, minced 1 Tablespoon cilantro, chopped Salt and freshly ground black pepper
For tuna 1-1/2 teaspoons chile powder 1/2 teaspoon ground cumin 1/4 teaspoon kosher salt 1/4 teaspoon ground black pepper 1 garlic clove, minced 2 yellow-fin tuna steaks Olive oil
Rinse tuna steaks and pat dry.
With a mortar and pestle, combine chile powder, cumin, salt, pepper and garlic, grinding mixture into a "wet" powder.
Rub mixture all over tuna steaks. Let sit for 15 minutes. Spray or lightly brush both sides of tuna with olive oil.
Preheat grill. Using a food processor, combine sour cream, water, lemon juice, chives, shallots, and cilantro, blending until mixture just turns pale green. Transfer to a bowl and adjust seasonings to taste with salt and freshly ground black pepper.
Grill tuna steaks over medium-high flame for 2-1/2 minutes per side. Transfer to a plate. Tent loosely with foil and let rest for 5 minutes.
To serve, spoon several tablespoons of sauce onto plates. Cut tuna against grain into 1/2 inch thick slices (tuna should be pink in center). Lay several tuna slices on top of sauce. Serve.