In a large saucepan, combine orange, cherries, juice. Bring to a boil over medium-high heat. Reduce heat, cove and boil gently, stirring frequently, until peel is tender,about 20 minutes. Maintaining boil, gradually stir in sugar. Boil hard, stirring frequently, until mixture reaches gel stage, about 30 minutes. Remove from heat and test gel. If gel stage has been reached, skim off foam.
Ladle hot marmalade into hot jars, leaving 1/4 in headspace. Remove air bubbles and adjust headspace, if necessary by adding more marmalade. Wipe rim and put on lids and bands.
Place jars in canner, bring to a boil and process 15 minutes.