You can check if the pork back is done to your preference by using a meat thermometer.
If the core temperature reaches 70-75°C (158-167°F) the meat is medium-well. If its core temperature reaches 80-85°C (176-185°F) it is well done, but not as tender anymore.
In addition, you may also use the juice from the baking tray to make a delicious gravy sauce or simply pour it over the vegetables you may have made as a side dish.
For a sauce, simply fry 2 onions with butter in a pan (until golden brown), then pour in the meat juice and let everything cook until it is reduced to your desired thickness.
If you don’t want to use onions, replace them with 100ml (about 3oz) cream in order to get thickness to the sauce.