In a medium mixing bowl, combine the drained canned tuna, mayonnaise, finely chopped celery, diced red onion, and fresh herbs. Add Dijon mustard, salt, and pepper to taste. Mix well until all ingredients are thoroughly combined, achieving a creamy texture.

Slice the ripe avocados in half lengthwise and remove the pit. Brush the exposed flesh with lemon juice to prevent browning. Arrange the avocado halves on a serving platter.

Spoon the tuna mixture generously into each avocado half, pressing down slightly to ensure it adheres to the avocado.

Serve the Tuna Stuffed Avocados immediately as a light lunch or snack.