In a medium mixing bowl, combine the tuna, celery, Kewpie mayonnaise, shallot, lemon zest, lemon juice, pepperoncini brine, Dijon and capers. Mix until well combined and season to taste with salt and pepper.
Spread the tuna salad onto the bottom half of the bread and top with the pepperoncini peppers. Close each sandwich and cut in half. Serve.
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Notes
Make sure you use both the lemon zest and the juice! The zest adds concentrated citrus aroma without extra liquid, giving the tuna salad a brighter, fresher flavor that really sets this recipe apart.