Hold the chayote in a paper towel or under running water and peel. All of the peel will likely not come out of the grooves, it's fine.

Cut squash into quarters and remove the seed (optional). Lay flat side down on cutting board and slice a bit smaller than 1/4" thick

Put a heavy frying pan over medium heat, when hot add butter and onion and half of the salt. When onions are beginning to be translucent add squash, salt and oregano to the pan.

Cover pan and reduce heat to low, cooking until tender, about 10 - 12 minutes. You don't want the chayote mushy but you do want them to be tender when poked with a fork.

Serve and enjoy!