How do I recover a phone contact from my iPhone 12 that I accidentally deleted about 8 months ago

There’s no way to do that. Not with contacts stored in iCloud or some other server. No service keeps deleted info that long*.

Ask the contact, or a mutual acquaintance.

*If the contacts are kept local—they’re almost certainly not—and if you have an eight month old backup still around, then you can potentially back up your current environment, remove your SIM and shut off your Wi-Fi router to avoid re-syncing old data, restore the old backup, copy off the contact info, and re-restore the backup of the current environment… But you don’t have an eight month old backup, likely are not using local storage for contacts, and probably don’t want to risk reloading and resetting your entire environment with old data anyway.

After 8 months the contact is almost certainly gone from any backups which might have retained the data. Your best hope is to look through places like old emails or iMessage, where you might find enough in somebody's signature to let you build a new contact.