Preheat the oven to 425ºF and line a large sheet pan with foil or parchment for easy cleanup.

Cut the chicken into 1-inch pieces and place in a large mixing bowl. Add the brown sugar, smoked paprika, garlic powder, onion powder, cayenne, kosher salt, and 1 tablespoon olive oil. Toss until the chicken is evenly coated. Add lemon slices and gently mix to distribute.

Spread the chicken and lemon slices in a single layer on the sheet pan. Roast for 15 minutes.

Use a spatula to flip or toss the pieces so they brown evenly. Roast an additional 4–7 minutes until edges are caramelized and internal temperature reaches 165ºF.

While the chicken roasts, make the herby ranch slaw: in a medium bowl whisk together the ½ cup yogurt, chopped dill, parsley, chives, juice from ½ lemon, 2 tablespoons olive oil, and a pinch of kosher salt. Taste and adjust salt or lemon as needed.

Fold the shredded cabbage into the dressing until well coated. Let the slaw rest for 10–15 minutes so the cabbage softens and flavors meld.

Warm the pitas: place them in a low oven for a few minutes, or wrap in foil and heat, or microwave briefly under a damp paper towel until pliable.

Assemble: open each pita, spoon in a generous amount of slaw, add several pieces of roasted chicken, and top with cubed avocado. Serve immediately.