Rinse and drain the tuna and place into a large mixing bowl.
Using a fork, break up the tuna so that most of the chunks are gone and it is completely shredded.
Mix in the mayo, ketchup, pickles, sea salt and black pepper.
Fill each butter lettuce leaf with approx. 3 tbsp tuna, top with a few cilantro leaves, 1-2 slices of cilantro and serve!