Pat the chicken dry and season both sides with 1 tsp salt, 1/2 tsp black pepper, and 1/2 tsp garlic powder. Heat 1 tablespoon olive oil in a skillet over medium-high heat. Add the chicken and cook 4–6 minutes per side (depending on thickness) until golden and internal temperature reaches 165°F (74°C). Alternatively, bake at 400°F (200°C) for 18–22 minutes.

Shred the chicken

Transfer cooked chicken to a plate, let rest 5 minutes, then shred using two forks or chop finely. Return shredded chicken to the skillet over low heat.

Make BBQ chicken

To the shredded chicken in the skillet add 3/4 cup BBQ sauce, 1 tablespoon apple cider vinegar, and 1 tablespoon brown sugar (if using). Stir to combine and warm through 2–3 minutes so the sauce coats the chicken evenly. Taste and adjust seasoning; add a pinch of salt or more BBQ sauce if desired. Keep warm off the heat.

Pickled Red Onion

Combine 2 tablespoons apple cider vinegar, 2 tablespoons water, 1/2 teaspoon sugar, and 1/4 teaspoon salt in a small bowl. Add the thinly sliced 1/2 cup red onion, toss to submerge, and let sit at room temperature for at least 10 minutes (or refrigerate up to 2 hours). Drain before using. Quick pickling mellows the onion’s bite and adds bright acidity to the flatbread.

Flatbread Assembly

Preheat and prepare flatbreads

Preheat oven to 425°F (220°C) with a rack in the middle. Place 2 flatbreads on a baking sheet lined with parchment. Lightly brush each flatbread with melted butter or olive oil (about 1/2 tablespoon per flatbread) to promote browning and crisping.

Assemble flatbreads

Divide the BBQ-shredded chicken evenly between the two flatbreads, spreading it into an even layer but leaving a small border. Spoon any extra sauce from the skillet over the chicken for extra flavor. Sprinkle 3/4 cup mixed shredded cheese over each flatbread (total 1.5 cups) so cheese covers chicken evenly. Scatter pickled red onion evenly on top.

Bake

Bake the assembled flatbreads in the preheated oven for 8–10 minutes, until the cheese is melted and bubbly and edges are golden. If you prefer extra char, switch to broil for 1–2 minutes—watch closely to avoid burning.

Finish and serve

Remove flatbreads from oven. Sprinkle sliced scallions (3 tablespoons) and chopped cilantro (optional, 2 tablespoons) over the hot flatbreads. Let rest 1–2 minutes, then slice into 4 pieces each and serve immediately.