I used:
3 lbs organic onions
2 T olive oil
2 T butter
some salt
You also need:
Deep lidded oven proof pan
Some kind of timer
Preheat the oven to 425˚
Cut up your onions like this:
Heat up the oil and butter in a deep oven-proof pan with a lid (I use a cast iron dutch oven) then throw in the chopped onions and stir to coat with the oil. Sprinkle in some salt - I used about 1/2 teaspoon, but you can use more or none at all.
Put the lidded pan into the preheated oven. Yes mine looks like this. So much for getting the self-cleaning model.
Set the timer for 15 minutes.
You are going to stir the onions every 15 minutes for about 2 hours, so it's a good time to get stuff done around the house. Or watch movies on netflix.
They will go from looking like this:
To looking like this:
All done!
I put them into an ice cube tray to freeze in small portions for using in recipes, but I don't recommend you do this. They were really hard to get out after they froze. Next time I will probably just freeze separate little mounds on a sheet of freezer paper
Also a word of warning - this method will make your house smell like onions for days after. Best done on a nice day when you can open windows and when you aren't expecting company!