Prepare the grill for direct/indirect cooking or the two zone method using lump charcoal. Target 450 - 500 degrees over direct heat.
Trim the pork tenderloin by removing silver skin, and cut about 3/4 inch off the tail side of the tenderloin to make it an even thickness.
Coat the tenderloins with olive oil and apply the dry rub liberally.
Place the tenderloin over direct heat and sear one side for four minutes or until nice grill marks form. Flip the tenderloin and grill the other side over direct heat for an additional four minutes. Move to the indirect side, cover grill, and finish cooking, about 8 more minutes.
Remove the pork tenderloin when the internal temperature of the thickest part of the pork tenderloin reads 140 degrees Fahrenheit using a good quality instant read thermometer like a Thermapen MK4 from Thermoworks.
Let rest 10 minutes and make sage butter.
Sage Butter Sauce: In a small pan melt butter over medium heat. When melted, add the sage and continue cooking while sage fries and infuses with the butter.
Remove from heat after about 6 minutes or until the sage is slightly crispy. Slice the pork tenderloin in medallions, plate and pour butter over the slices. Add the crispy sage and enjoy.
For the Butter Sauce: feel free to add other herbs, like thyme or rosemary, if you like those flavors, for a different take on this decadent herb butter sauce.