Heat the oven to 475 degrees Fahrenheit (it will take at least 20 minutes to warm up). Make a glaze for the pork by combining two spoonfuls of chile powder with an equal amount of brown sugar, two generous pinches of salt, a few grinds of pepper, and a drizzle of olive oil in a bowl. Stir in enough coffee until the mixture is pourable.
Put a little olive oil in a baking dish and rub it around with a paper towel to thoroughly grease the dish.
Place the pork loin in the baking dish. Pour your glaze over the loin, and rub it over the meat to coat. Not all the glaze will stay on the meat—that’s OK.
Put the loin in the oven and set the timer for 20 minutes; it will turn brown and form a nice crust. Turn down the oven to 350 degrees Fahrenheit, and roast the loin for another 40 minutes.
Remove the loin from the oven and check its temperature with a meat thermometer. It should register about 150 degrees Fahrenheit. If it’s not that hot yet, put the pork back in the oven. When the internal temperature is 150 degrees Fahrenheit, remove the loin from the baking dish and let it rest for 10 minutes (the final temp should be about 160).
Slice the roast and serve.