- 1/4 cup mustard powder
- 2 tablespoons hot water
- 2 tablespoons unseasoned rice vinegar
- 1/4 cup soy sauce
- 1 1/2 tablespoons paprika
- 1/2 tablespoon cayenne pepper
- 1/2 tablespoon chili powder
- 1/4 tablespoon freshly ground pepper
- 8 ounces ahi tuna fillet
- Make the soy-mustard sauce by mixing the mustard powder and hot water together to form a paste. Let sit for a few minutes to allow the flavor and heat to develop; then add the vinegar and soy sauce, mix together, and strain through a fine sieve. Chill the sauce in the refrigerator.
- Combine the paprika, cayenne, chili powder, and pepper on a flat plate to make the blackening spice; then dredge the tuna in the spice.
- Heat a lightly oiled cast-iron skillet over high heat and sear the tuna fillet to the desired doneness (about 15 seconds per side for rare, 1 minute per side for medium-rare).
- Cut the tuna into 16 thin slices and arrange four slices in a pinwheel or cross shape on each plate. (or you can cut it into thicker slices.) Ladle some sauce around the plate.