Are you asking how to find such a recipe in EYB, or for one that other users have personally tried?
If the former: Search in the Library recipes using the Recipe Type filter of 'Preserves/Jams, jellies, & preserves', put 'red onion' in the search text, and check the box for 'Online recipes'. There are 25; most are jams rather than jellies.
If the latter, can't help as I've never made onion jelly or jam, but sounds like a delicious dish. Best luck, either way.
