Place tomatillos and jalapeño on a hot cast-iron skillet or under a broiler and char until blistered and softened, about 5–7 minutes, turning once. Remove and let cool slightly.

Transfer charred tomatillos and jalapeño to a blender. Add cilantro leaves, garlic clove, lime juice, cold water, olive oil, and kosher salt. Blend on high until smooth and bright green, about 30–45 seconds. Adjust seasoning with more salt or lime to taste. Chill while preparing other components.

Guajillo Marinade for Vegetables

Rehydrate and puree

Place dried guajillo chilies in a heatproof bowl and pour 1 cup hot water over them; let soak 15 minutes until softened. Drain, reserving about 2 tbs soaking liquid. Transfer chilies to a blender with garlic clove, reserved soaking liquid, lime juice, olive oil, honey, smoked paprika, and kosher salt. Blend until smooth, about 30 seconds. Taste and adjust salt or honey if needed. Strain if you want a smoother marinade.

Lightly Marinated Vegetables

In a medium bowl combine cucumber ribbons, radishes, red onion, and halved cherry tomatoes. Add 3 tbs of the prepared guajillo marinade, 1 tbs fresh lime juice, and 1 tsp sea salt. Toss gently to coat. Let sit at room temperature for 10–15 minutes to lightly marinate, then drain any excess liquid just before plating.

Ahi Tuna

Pat the tuna loin dry with paper towels. Season all over with 1 tsp kosher salt and 1 tsp freshly ground black pepper, pressing seasoning to adhere.

Sear

Heat a heavy skillet (cast-iron preferred) over high heat until smoking hot. Add 2 tbs neutral oil and swirl to coat. Place tuna in the pan and sear 30–45 seconds per side for a rare center (adjust to 60–90 seconds per side for medium-rare). Use tongs to sear edges for 10–15 seconds to render any thin fat. Remove and rest on a cutting board for 2 minutes.

Using a very sharp knife, slice tuna crosswise into 1/4-inch thick slices. Arrange slices slightly fanned on chilled plates or a serving board.

Finishing & Assembly

Spoon a thin smear or pools of the chilled aqua chili verde on the plate beneath and around the arranged tuna slices (about 2–3 tbs sauce per plate).

Top tuna slices with a small mound of the lightly marinated vegetables (about 2–3 tbs per portion).

Drizzle 1 tsp extra-virgin olive oil over the tuna, sprinkle toasted sesame seeds, scatter tiny cilantro leaves and microgreens as desired.

Serve immediately while tuna is still slightly warm in the center and vegetables are crisp. Provide extra aqua chili verde on the side if desired.