Roughly chop the apples (including the skin and core) and put them in a large heatproof bowl. Add the cider and lemon rind, then partially cover the bowl with microwave cling-film. Microwave on high for 10 to 12 minutes until the apples are soft, stirring twice during cooking. Puree the apples in a food processor then pour into large nylon sieve placed over a bowl; leave to drip for 2 hours. Set the drained pulp aside for the apple and rum spread. Measure the apple juice there should be about 1/2 pint but if necessary make up to half a pint with some cold water. Pour the apple juice into a medium-sized heatproof bowl and stir in the sugar. Microwave uncovered on high for 8 to 9 minutes until a teaspoon of the jelly dropped on to a chilled saucer forms a skin after 1 minute. Carefully pour the jelly into a clean warm jar and cover with a waxed paper disc. Allow to cool then cover with a lid. This recipe yields approximately 12 ounces.