You can create a registration form containing only an Email Field using Beaver Builder and Ultimate Addons for Beaver Builder!
Firstly you will need to drag and drop a User Registration Form module on the Beaver Builder Editor and remove all the default Form Fields except the Email field.
Now, under the After Register Actions section under the General tab, enable the Send Email option, this would – send the new user an email about their successful account creation.
On enabling this option, an Email tab will be visible on the fourth tab, under which you will be able to customize your email template which will be sent to the User.
Here you will find the following shortcode [PASSWORD] this would send the user the Password in the email.
The user can use the Password received in the email and email used to log in to your website.