In a large skillet over medium heat, brown pork chops on both sides. Remove chops and place them in a shallow baking dish.
Combine the ketchup, brown sugar, and vinegar. Pour mixture over chops, spreading to cover evenly. Cut 6 slices from the lemon, and lay one slice on top of each chop. Squeeze the juice from the remaining portion of lemon over the chops.
Cover and bake for 30 minutes at 325 degrees F (165 degrees C). Uncover and bake for 10 minutes more.