Place the chicken breast between two sheets of parchment paper and pound to an even half-inch thickness.
Season the chicken on both sides with sea salt, black pepper, garlic powder, and smoked paprika.
Set up three shallow bowls: one with whole wheat flour, one with the whisked egg white, and one with panko breadcrumbs.
Dredge the chicken in the flour, dip into the egg white, and then press firmly into the panko crumbs until fully coated.
Lightly brush or spray the chicken with avocado oil and air fry at 400 degrees Fahrenheit for 12 to 15 minutes, flipping halfway through, until crispy and cooked through.
In a small bowl, whisk together the Greek yogurt, Dijon mustard, and lemon juice to create the tangy aioli.
Toast the whole wheat bun until lightly browned.
Spread the aioli on both sides of the bun, then layer the butter lettuce, tomato slices, and the crispy chicken breast to assemble the burger.