In a small pot or a microwave-safe bowl, combine the bourbon, brown sugar, and soy sauce. Heat over low heat for a few minutes, stirring often, until the brown sugar is dissolved — or do this in the microwave, working in 20-second bursts. Stir in the Worcestershire sauce, lemon juice, thyme, and pepper. Allow to cool completely.
Place the marinade in a large sturdy zipper top bag or a container big enough to hold the meat. Add the marinade and turn the pork to coat well. Cover, and place in the fridge to marinate overnight, or at least 6 hours.
Preheat the oven to 425 F. Cover a rimmed baking sheet or a baking pan with foil, wrapping it well to enclose the whole pan (see Note). Place the pork on the baking sheet or pan, and roast for about 15 to 30 minutes (it really depends on the thickness of the pork loin), until a meat thermometer registers 145 F. If you have the inclination, baste it after 10 minutes with any extra marinade. Let the pork sit on a cutting board for 10 minutes before slicing it.
Here’s the most important thing to remember. Cover your rimmed baking sheet with foil. Cover the whole dang thing, wrapping the foil up and over the edges. The marinade will give your pork a lovely brown crust, but the part that stays on the pan will probably burn. And that is not a fun thing to clean off a pan.
If you want to use a pork loin instead of a tenderloin, know that you will have to increase the cooking time. You will still be looking for an internal temperature of 145 degrees, but pork loins are significantly thicker than tenderloins and, therefore, will take longer to roast.