This one sounds insane, but hear me out. Submerge your whole half-avocado (skin on) in a bowl of cold water. Stick it in the fridge.
The water creates an airtight seal. No oxygen, no browning. I’ve kept a half-avo fresh for four days this way. When you pull it out, it looks like you just cut it.
Here’s the catch: the texture gets a tiny bit watery on the surface. Pat it dry with a paper towel before eating, and you won’t notice. Your future-sandwich self will thank you.
3 Ways to Preserve Avocados - wikiHow Life