Heat a large frying pan over high heat. Sear the pork chops until browned, 1 to 2 minutes per side. Transfer the pork chops to a slow cooker. Mix the brown sugar, tomato sauce, onion and lemon juice in a bowl; spoon over the pork chops.
Cook on Low until the pork chops are very tender, 4 to 6 hours.
For quicker cooking, you can also bake them in the oven for 30 minutes at 180 degrees C.