Combine half of the orange and half of the lime juice in a large bowl.
Then add the ground coriander and the ancho pepper powder.
Add the steak to the marinade and let them stand at room temperature for 15 minutes.
In a small pot, combine the remaining juices of lime and orange with sugar and apple cider vinegar and 2 tablespoons of water.
Bring it to a simmer and let it simmer for ½ minute. Then add the sliced onions and let it rest at room temperature, tossing occasionally.
Heat the oil in a medium skillet until hot, add the steak, previously removed from marination, and sear for 30 sec on each side to desired wellness.
Remove steak from skillet and sprinkle with salt.
Allow the steak to rest for two minutes prior to slicing into thin slices.
Warm the tortilla and start to assemble the tacos with thin slices of steak, pickled onions, sliced avocado, and drizzle with sour cream and fresh coriander leaf.