Bring a medium saucepan filled with water to a boil. Squeeze half of the orange and half of the lime into a large bowl and add the coriander, cumin, 1/2 teaspoon ancho powder and 1 teaspoon salt. Poke the steak all over with a fork and add it to the bowl, turning to coat; marinate at room temperature for 15 minutes.
Meanwhile, combine the juices from the remaining orange and lime halves in a medium microwave-safe bowl with the cider vinegar, sugar, 1/4 teaspoon salt and 2 tablespoons water. Microwave until simmering, about 45 seconds. Add the red onion and let stand, tossing occasionally, until ready to serve.
In a small saucepan, combine the paprika with 1/2 cup oil and the remaining 1/2 teaspoon ancho power. Bring to just below a simmer over medium-low heat and cook, stirring occasionally, until the oil is hot and bright red, about 3 minutes. Transfer to a small bowl.
Prepare a large bowl of ice water. Add the cilantro and parsley to the boiling water and cook until just bright green and wilted, about 20 seconds. Quickly transfer to the ice bath to cool. Remove the herbs from the water and squeeze out as much of the water as possible. Place in a blender with the remaining 1/2 cup oil and blend on high until as smooth as possible. Strain through a fine-meshed sieve into a small bowl.
Heat a little vegetable oil in a large cast-iron pan over medium-high heat until very hot. Remove the steak from the marinade and pat dry. Cook the steak, turning once, until well-seared on the outside and medium rare, 5 to 6 minutes per side. Transfer the steak to a cutting board and let rest 5 minutes; thinly slice across the grain. Sprinkle with additional salt.
Adorn 4 plates with some crema and the chile and herb oils. Make 3 steak tacos per person, topping the tortillas with pickled onion, avocado, cilantro a drizzle of crema and some chile and herb oils.