In a medium bowl, whisk together the vinaigrette ingredients: extra virgin olive oil, lemon zest and juice, orange zest and juice, and caper juice. Season with salt and pepper.

Carefully slice the sushi-grade ahi tuna into thin, bite-sized pieces, about 1/4 inch thick, and arrange on a chilled serving platter.

Wash and slice the Persian cucumber into rounds or half-moons, and arrange on top of the tuna.

Drizzle the prepared vinaigrette generously over the tuna and cucumber, ensuring even coverage.

Finish by sprinkling toasted sesame seeds, flaky salt, and black pepper over the dish before serving.