In a blender, add the serranos, white onion, garlic cloves, cilantro, lime juice, orange juice and soy sauce.. Blend until smooth. Add the marinade to a bowl or food safe bag, then add your cumin, garlic powder, black pepper, salt and canola oil. Mix together and add your steaks to marinate. Let marinate for at least 12 hours but up to 36 hours.
Preheat your grill to high heat for direct grilling (around 400F).
Add a cast iron skillet to the grill and get it very hot. Add your tomatillos, garlic cloves and onion to char for 2-3 minutes. Once they are charred, add them to a blender with your chipotle in adobo. Blend till smooth, then add your salt and sugar as needed. Keep warm and set to the side until ready to serve.
Pull your steaks out from the fridge and let sit at room temperature for 15 minutes. Add your steaks to the grill and cook for about 4 minutes per side or until they are 125F internal. When done, pull the steaks off and rest for 5 minutes. When ready, slice the steaks against the grain and into cubes. (Optional): For more char flavor, add your cubed steak back to the grill in a skillet and cook for another 2-3 minutes to get extra crispy. Pull off once done.
Preheat a skillet/plancha to medium high heat (about 375F). Grab a handful of freshly grated cheese and place it on the skillet about the same size as your tortilla. Repeat adding cheese to the skillet for your desired amount of taco shells. Next, add your tortilla over the top of the melting cheese, then carefully flip it over. Tip: use a nice spatula to get the cheese to release. Continue cooking the tortilla until it begins to get hard (about 2 more minutes). Pull off once done.
Top each taco with a heaping handful of steak, red onion, chopped cilantro, sour cream, chipotle salsa and guacamole. Serve and enjoy!