Prepare the pork tenderloin by placing the meat on a baking sheet. In a small bowl, stir together the salt, pepper, mustard powder, and ancho powder until combined. Liberally sprinkle the seasoning mixture over all sides of the pork and rub into the meat, using all the seasoning.
2 lbs. pork tenderloin, 2 Tablespoons kosher salt, 2 Tablespoons freshly ground black pepper, 1 Tablespoons mustard powder, ½ Tablespoon ancho powder
Heat a large cast iron skillet over high heat until smoking, then add the olive oil and let it heat for 30 seconds before adding the pork to the skillet and searing on all sides until brown, about 1 minute per side.
2 Tablespoons olive oil
Once the pork is seared, transfer it to a sheet pan and brush it liberally all over with a glaze made by stirring together the mustard, honey, Sriracha, vinegar, and salt & pepper in a bowl. Roast for 8 to 10 minutes, or until medium done and a meat thermometer inserted into the middle of the tenderloin registers between 145°F and 150°F.
½ cup dijon mustard, ½ cup honey, 1 Tablespoon Sriracha, 1 Tablespoons cider vinegar, Salt and freshly ground black pepper
Remove pork from oven and allow to rest for 10 minutes before slicing.