This is totally do-able!
- Create new ONTRAform or ONTRApage
- Include the Email address field
- Navigate to Form Settings and check the box at the bottom that says "Override email address merge with cookie data" - screenshot
- Publish the Form or Page
- Grab the link and place it in an email. Email links cookie contacts when they click through them, so when they're taken to the update form, it will update their specific contact record.
Pretty easy right?