In a small mixing bowl, mix together the mayo, lemon juice, chives, celery and season with salt and pepper. Add in the tuna, gently stirring to combine and set aside.
Place a small skillet over medium heat. While the skillet is heating, butter the sides of the roll and add to the skillet, cooking until golden brown on each side, about 1-2 minutes.
Remove the roll from the skillet and gently pile in the tuna mixture. Sprinkle some extra chives on top along with a little lemon zest.
Makes 1 roll