1) Preheat oven to temperature of 355 degrees.
2) From the gammon rashers, remove the rind and snip the fat at 1/2-inch intervals. This will prevent the meat from buckling when being cooked.
3) In a casserole dish, place the rashers and top each rasher with a pineapple ring. From the tin, add 2-3 tablespoons of juice.
4) Cover the casserole with a li and put it in the preheated oven's center. Bake for 1 hour.
5) Serve hot with pineapple rings and some juice from the casserole dish.