Pat the ahi tuna dry with paper towels. Trim any connective tissue. Cut the tuna into 1-inch cubes (yielding approximately 24-30 bites from 1 lb). Keep the tuna cold in the refrigerator while you make the spice rub.

Make the blackening spice

In a small bowl combine paprika, smoked paprika, onion powder, garlic powder, dried oregano, ground cumin, cayenne pepper, kosher salt, and black pepper. Mix thoroughly to create an even rub.

Coat the tuna

Drizzle the tuna cubes with 2 tbs olive oil and toss gently to coat. Sprinkle the blackening spice over the tuna and toss just until pieces are evenly coated on all sides. Do not overwork the tuna.

Sear the tuna

Heat a large heavy skillet (cast iron recommended) over high heat until very hot, about 2–3 minutes. Add 2 tbs neutral oil and swirl. Working in a single layer (in two batches if necessary), add the tuna cubes and sear 20–30 seconds per side to create a blackened exterior while keeping the center rare. Use tongs or a spatula to turn; do not overcrowd the pan. Remove seared bites to a wire rack or plate.

Finish

If using toothpicks or small skewers, thread 2–3 cubes per pick. Sprinkle lightly with sesame seeds and a pinch more salt if desired. Keep warm while you prepare plating components.

Lemon Garlic Aioli

In a small bowl, combine mayonnaise, minced garlic, lemon juice, lemon zest, Dijon mustard, and extra-virgin olive oil. Whisk until smooth. Season with salt and freshly ground black pepper. If the aioli is too thick, whisk in up to 1 tablespoon water to reach a smooth, dipping consistency. Taste and adjust lemon, garlic, or salt to preference. Refrigerate until ready to serve.

Condiments & Serve

Char the lemons: place lemon halves cut-side down on a hot, dry skillet or grill over medium-high heat. Press gently and cook 2–3 minutes until well-browned and slightly caramelized. Remove from heat.

Plate the bites: Arrange the blackened tuna bites on a serving platter or individual plates. Spoon a dollop of lemon garlic aioli beside the tuna. Place a small smear or quenelle of wasabi paste on the plate (or serve in a tiny bowl) so guests can add heat to taste.

Garnish and finish: Garnish with microgreens or chopped chives and a light sprinkle of sesame seeds. Add the charred lemon halves to the platter for squeezing over the tuna. Serve immediately so the tuna remains warm and the center stays rare.