There's no way to delete your account.
From their FAQ:
Can I delete my account?
Yes, but not at the moment. This is coming very soon.
LOL! Anyway, try to post an account removal request in the help group: http://www.grouprecipes.com/group/help-group/1678
Because an account at Group Recipes cannot be deleted, we suggest to make your data useless.
Be logged in on the site, then go to Profile Settings (Or Options, etc.). In all fields with personal data (such as name, address, city), fill in AccountKiller, if possible. If you can only choose from several options, change the value. If possible, use a homepage/URL field or long text field (such as Description) and put this line in it: https://www.accountkiller.com/removal-requested. This may incite webmasters to add an account deletion option.
If you can't find any contact info and still wish to ask something, for example a question about what exactly is deleted, about data retention, etc., you may contact the domain owners using this info.
If you signed up for Group Recipes using a third-party login such as Facebook or Twitter, you probably want to revoke all access from Group Recipes. Click the icon below to find out how.