Thinly slice the mini cucumbers into 1/4-inch rounds and set aside in a small bowl. Thinly shave the red onion, cutting against the grain to create delicate pieces that will have a milder bite than thicker slices. I like to soak the shaved onions in a bowl of ice water for a few minutes to soften their sharp flavor and add a nice crisp texture to the wraps.

Pat the chicken breast dry with paper towels to remove excess moisture, which helps the blackening spice crust develop properly. Heat a cast-iron skillet or heavy-bottomed pan over medium-high heat until very hot, then sear the chicken breast on each side until deeply browned and cooked through, about 6-7 minutes per side depending on thickness. Let the chicken rest for 3-4 minutes, then slice it against the grain into strips.

Place 6 large Bibb or Butter lettuce leaves on serving plates as your edible vessels. Layer the sliced chicken from Step 2 down the center of each leaf, then top with the cucumber slices and red onion from Step 1. Drizzle each wrap with approximately 1 tablespoon of tzatziki sauce, and finish with a sprinkle of fresh dill and a light squeeze of lemon juice to brighten all the flavors together.