Open and drain your cans of tuna. Place in a bowl and fork until all the tuna is broken apart. Set aside.
Now prep and chop your celery, red onions, green onions and dill. Add in the bowl with the tuna. Add lemon juice, mayo, dijon mustard and salt and pepper. Mix well. Adjust with more lemon juice if preferred (I personally like my tuna really lemony so I’ll add more)!
Store in the fridge for up to 30 minutes to allow all the flavors and juices to combine. Remove and top with parsley and serve with butter lettuce.