Shredded chicken:

Preheat the oven 180ºC.

In a small bowl, mix together the chilli powder, cumin, salt, garlic powder, pepper and smoked paprika. Mix it together.

Bake until cooked through, 35 - 40 minutes.

In a small saucepan, whisk together vinegar, 1 cup water, sugar and salt. Bring to a boil over medium heat and then let simmer for 5 minutes.

Remove the brine from the heat and carefully pour it over the onions. Let sit for at least 1 hour, then cover and refrigerate until ready to use.

To finish :

In a medium skillet over medium high heat, char the tortillas for 1 minutes on each side, until browning begins. You want the tortillas to still be malleable, not hard or crispy.