How do I get client side to download a link generated by API response?

My situation is that I have a webpage with a form that the user fills out. When the form is submitted, my server processes the form to generate a 3rd party link that is on the CDN.

Currently I am downloading the image on my server and then sending it the client. However, I want to save on bandwidth costs and would rather just send the CDN link back to the client and have him initiate the download instantly, with out any other interactions from the user. How can I do that?