In a large bowl, mix together the sweet potato, salmon, dill, lemon juice, salt, pepper and mayo until fully incorporated.
Fold in the diced green onions.
Divide the salmon mixture into six mounds. Flatten slightly and form into patties. Place patties on parchment lined plate and chill for 20-30 minutes.
Spread coconut flour on large plate. Press each side of the chilled patties into coconut flour and dust off the excess.
Heat a large cast iron pan over medium and add avocado oil. When pan is hot, add salmon patties. Cook for 3-4 minutes each side until lightly browned and the middle is firm.
Place patty in butter lettuce leaf cup, top with tomato and cucumber tzatziki.