Remove the meat from the chicken, then use your fingers to pull any larger chunks into bite-size pieces.
In a medium saucepan over medium heat, combine the chicken, coconut milk, cumin, lime zest and juice, and hot sauce. Simmer until heated through and thick.
Season the chicken with salt and pepper, then remove from the heat. Stir in the cilantro, then divide the mixture between the tortillas.
Top each serving with diced onion and avocado. Serve immediately.
