I am Canning some of my onions, these are so good you can eat them on sandwiches or just warm up to eat like fried onions.
First I started with a large pan of onions.
Peeled off the skins
Slice in half.
Then cut into slices.
I filled a large roaster pan with the sliced onions and two sticks of butter or margarine. I did end up adding one more stick of butter add as much butter as needed to keep from sticking.
I cooked it for several hours as you can see it reduces down a lot about 3/4 and very browned. Then put in your pint jars you do not need to add anything else. Put your lids and rings then pressure can for 75 minutes at 15 pounds or what your owners manual recommends for your altitude
As you can see they do get a little darker in the canner. I have always warmed them before I use them. A great way to keep your onions