I have a lot of peppers and onions can I chop them up and freeze them and then use them in canning salsa and stewed tomatoes later? I would measure them first before freezing, like one cup.
Yes you can. Many of us dice the onions and freeze them in 1 or 2 cup packs for later use. Peppers are usually cored and de-seeded then laid out on a cookie sheet and individually frozen in 1/2 or quarters or large chunks depending on their size. Once frozen just put all of them into a ziplock bag.
You can dice them but they will be mushy when thawed so the larger pieces are easier to work with.
I dice some peppers so I can just knock out what I need for soups, etc.
I learned my lesson about being too frugal trying to save on bags. I chopped onions and froze in a gallon ziploc. By the time I used them up, they had pretty well frozen into a solid block from the bit of thawing each time I took them out of the freezer. It didn't really pay to save a few bags. Smaller sizes are easier to work with!
You can stuff the peppers and freeze them too!
Otherwise.........what Dave said!! LOL
I chop peppers/onions & freeze on cookie sheet before bagging too.. :-)