Preheat your oven to 400°F (200°C). If you have a pizza stone, place it inside while the oven heats. Otherwise, prepare a large baking sheet by lining it with parchment paper for easy cleanup.
Place your flatbreads on the prepared baking sheet. If you like a very crispy crust, you can brush the edges of the flatbread lightly with olive oil. This helps the edges turn a beautiful golden brown while baking.
Spread about 1/4 cup of BBQ sauce evenly over each flatbread, leaving a small border around the edges. Sprinkle half of the mozzarella cheese over the sauce. Evenly distribute the shredded chicken and sliced red onions over both pizzas.
Place the baking sheet in the center rack of the oven. Bake for 10 to 12 minutes, or until the cheese is fully melted and bubbling, and the edges of the flatbread are crisp and golden.
Remove the pizzas from the oven and let them cool for a minute or two. Sprinkle the fresh chopped cilantro over the top. Use a pizza cutter or a sharp knife to slice the flatbreads into pieces and serve immediately.