SSL certificate

I build a website to make a website for each tenant with their domains I want to know what is the best of these two processes 1- create an SSL certificate and ask the tenant to add its CNAME to his domain provider 2- create a hosted zone and ask the tenant to change NS in his domain provider second process 1- create a hosted zone and ask the tenant to change NS in his domain provider 2 - create an SSL certificate and create Record in the hosted zone automatically