Hi @laurentdesserre, thanks for the post. At the moment, we do not allow 301 redirects for top level domains redirecting to a domain hosted in Webflow.
You should change the A Records on the domain and the CNAME record, the same as you did for the laurent.io domain.
This will also result in the benefit that both domains will be using the same fastly integration with hosting: Super Duper Fast Custom Domain Hosting - Webflow announcements - Forum | Webflow
http://help.webflow.com/faq/how-do-i-set-up-custom-domain-hosting-with-my-webflow-site
Remember to add the new domains laurentdesserrey.com and www.laurentdesserrey.com to the hosting tab in site settings.
After making those changes, republish your site. Let me know if any questions, or send an email to support@webflow.com. I am ready to help 
Cheers,
Dave