Canning method
Place alternate layers of sugar and rhubarb in a glass bowl. Let stand overnight.
In the morning, add the peeled apples and simmer for 1 1/2 to 2 hours.
Pour boiling hot marmalade into hot jars, leaving 1/4-inch headspace. Adjust lids.
Processing: Process half-pint jars for 15 minutes in a boiling-water canner. Yield: about 6 half-pints.