Fabienne's Fabulous Ahi Tuna Cups

Pat tuna steaks dry. Cut across the grain into thin slices; cut slices into smaller pieces.

Mix lemon zest and juice, onion, apple, endive, mayonnaise, mustard, honey, soy sauce, celery salt, and cayenne pepper together in a bowl. Incorporate the ahi tuna pieces. Refrigerate until time to serve.