I have been caning some of my onions. I can them in quart jars then when I open one I can keep it in the fridge to use out of until gone which in my house don’t take long as I cook a lot with onions.
First I peel a lot of onions.
Then I quarter them so they will fit in the food processor.
I chop them. I just love my food processor I would hate to have to do this by hand.
Then put in a big pan. And cover with water just to the top of the onions so they are covered.
I cook these down until translucent and fork soft.
I then put into my Jars liquid and onions leaving about a ¼ inch head space.
Put on your hot lids and rings.
Put in pressure canner ( do not water bath) and process for 50 minutes for quarts and 45 for pints at 15 pounds of pressure ( or what your canning book says for your altitude).
After your canner has cooled take out and let cool. The onions will be a darker color that is ok. Use just like you would a chopped onion in your cooking they are a little softer but not to much ( like a cooked onion).
I use to chop them ythen put in quart jars in the freezer but since I am trying to get away from freezers this works great.