In a medium bowl, whisk together the brown sugar replacement, garlic, 2 tablespoons of the avocado oil, mustard, vinegar, paprika, and chipotle powder until well combined. You will end up with a thick paste.
Heat the remaining 1 tablespoon oil in an ovenproof skillet over medium heat. Pat the tenderloin dry and sprinkle all over with salt and pepper.
Brown the tenderloin on all sides, about 4 minutes. Then spread all over with the garlic brown "sugar" paste.
Place the whole pan in the oven, uncovered, and cook 18 to 25 minutes or until the internal temperature of the pork reaches 140F.
Remove from the oven and let rest 5 minutes before slicing.