In a container with a tight-fitting lid, combine the onion with the vinegar, ice, and a generous pinch of salt. Close the container and shake to dissolve the salt. Refrigerate while you prepare the pork.
In a small bowl, whisk the chile powder with the paprika, cumin, garlic powder, coriander, 1 1/2 teaspoons salt, and 1 teaspoon pepper. Set the spice mixture aside.
Using a sharp knife, butterfly the pork tenderloin: Slice almost in half lengthwise, stopping about 1/2 inch from cutting through; open like a book on a work surface. Using your palm or a meat mallet, pound the tenderloin to an even thickness. Drizzle the pork with olive oil and season with the spice mixture.
Heat a large cast-iron skillet, grill pan or griddle over medium-high heat. Add the 2 tablespoons olive oil and then the pork. Cook, flipping once, until charred on the outside and the internal temperature reaches 140 degrees F, 6 to 8 minutes total. Transfer to a carving board and let rest for 5 minutes.
Meanwhile, warm the tortillas over an open flame or in the microwave; wrap in a clean kitchen towel to keep warm. Carve the pork against the grain and transfer to a platter. Serve the pork in the tortillas with sour cream, cilantro leaves, diced pineapple, hot sauce, and the pickled red onions.