At least a few hours and up to 1 month before you plan to cook, make the butter. In a small skillet over medium heat, heat the oil. Add the cilantro, shallot, and garlic and cook for 2 to 3 minutes, stirring often, until the shallot is soft. Transfer to a bowl and set aside to cool. In a medium bowl, cream the butter with a fork. Add the cilantro mixture and blend well. Transfer to a 12-X-12-inch sheet of waxed paper and form into a log about 8 inches long in the center of the sheet. If the mixture is too warm to handle, just refrigerate for a couple of minutes until it is ready. Roll the butter up in the waxed paper to make a firm log and twist the ends to hold it tight. Place in the freezer until firm.
One hour before you plan to cook, make the rub. In a small bowl, mix together the chili powder, salt, granulated garlic, onion powder, and smoked paprika. Add the oil and mix well. Place the steaks on a big platter and brush the wet chili rub evenly on both sides on the steaks. Refrigerate until it is time to cook.
Prepare the grill for cooking over direct medium-high heat. Place the steaks directly over the cooking grate. Cook for 4 to 5 minutes per side for medium-rare, or to your desired degree of doneness. Remove to individual serving plates and top each steak with a couple of thin slices of the butter. Let rest for 5 minutes before serving.