Soak hardwood chips in a bowl of water.

Toast cumin, fennel, and mustard seeds in a dry cast iron skillet until they begin to smoke (about 5 minutes).

Combine the toasted seeds and the remaining dry ingredients (except pork) in a spice grinder, mortar and pestle, or food processor.

Grind the ingredients to a powder.

Coat the pork tenderloin with the spice mixture.

Refrigerate for at least 30 minutes.

Prepare a charcoal grill.

When the coals have turned amber and become ashy on the outside, push them to one side.

Remove the hardwood chips from the water and pile them on top of the coals.

Position the grate on the grill and heat until the chips begin to smoke (about 10 minutes).

Sear the tenderloin over the coals on each side for 3 minutes.

Move the tenderloin to the side of the grill with no coals.

Cover the grill and cook for 5-10 minutes, or until the internal temperature reaches your desired doneness.

Let the tenderloin rest for 5 minutes before slicing and serving.