In a large bowl, make the marinade by combining the soy sauce, olive oil, brown sugar, mustard, bourbon, cajun seasoning, garlic and herbs. Reserve ⅓ cup.
Place meat into the bowl and marinate in the fridge for at least 20 mins (up to overnight). Preheat the grill, griddle, or grill pan.
Grill for 10 mins on one side.
And for an additional 10 mins on the other side, or until the internal temperature of the meat reaches 130 F at the thickest part.
While the meat is grilling, prepare the glaze. Place the reserved marinade in a small pot and bring to a boil. Reduce the heat and let it simmer until it begins to thicken. Whisk in the butter and reserve.
Let the meat rest for about 7-10 mins before slicing it. Slice it and brush with the glaze. Serve warm.