Getting started with Confluence Data Center on Azure suggests in the Additional steps required for SSL section that you need to set up SSL between the application gateway and Synchrony by linking to Overview of end to end SSL with Application Gateway, which specifically addresses configuring backend SSL.

However, this is inaccurate, and configuring SSL on between the load balancer and Synchrony can actually break the connection, since Synchrony does not support SSL natively (see Possible Confluence and Synchrony Configurations). This link should be removed, or updated to a different Azure doc that is not about configuring SSL behind the load balancer.