Pat the yellowtail dry with paper towels. Using a sharp knife, slice the yellowtail into 1/2-inch (1–1.2 cm) cubes or bite-size pieces. Place the cut fish in a non-reactive bowl.

Pour the combined lime and lemon juice over the fish so pieces are just submerged. Sprinkle the kosher salt and freshly ground black pepper over the fish and gently toss to coat. Let sit at room temperature for 8–12 minutes to lightly 'cook' in the citrus (shorter for more tender, raw texture; longer for more cured). Reserve the citrus used for the cure — you will taste and adjust the leche de tigre later if needed.

Leche de Tigre (marinade)

While the fish cures, prepare the leche de tigre. In a small bowl combine fish stock (or clam juice), fresh lime and lemon juices, minced shallot, chopped cilantro, and ají amarillo paste or minced serrano. Whisk in 15 ml extra-virgin olive oil and season with 1/4 teaspoon sea salt. Taste and adjust acidity, heat, and salt — the leche de tigre should be bright, slightly spicy, and balanced.

After the fish has cured 8–12 minutes, drain off about half of the curing citrus from the fish (reserve a splash). Add the prepared leche de tigre to the cured fish and gently fold to coat. Let marinate together 2–4 minutes—this deepens flavor without over-cooking the fish.

Vegetables & Garnishes

While the fish rests in the leche de tigre, halve the cherry tomatoes and very thinly slice the red onion. If using avocado, dice it and toss with a teaspoon of lime juice and a pinch of salt to prevent browning.

Gently fold the cherry tomatoes, sliced red onion, and (optional) diced avocado into the fish and leche de tigre mixture. Taste and adjust seasoning — add a splash of reserved curing citrus if you want brighter acidity, or more salt if needed.

Lemon Oil & Finishing

Make the lemon oil: in a small bowl whisk together 45 ml extra-virgin olive oil with the grated lemon zest and 1/4 teaspoon fine sea salt and 1/4 teaspoon freshly ground black pepper. Let rest 2 minutes so the zest infuses the oil, then taste and adjust.

To serve: transfer the cured yellowtail mixture to chilled plates or a shallow bowl. Drizzle the lemon oil over the ceviche (about 1 tablespoon per serving). Scatter fresh cilantro leaves and microgreens or baby arugula on top as garnish. Serve immediately with tortilla chips, cancha (toasted corn), or thinly sliced toasted baguette.

Leftovers: keep refrigerated in an airtight container up to 12 hours, but note texture will continue to firm as citrus cures the fish further—best eaten the same day.