How can you restore an Azure VM Backup to a different data center?

You can only backup/restore VMs within the same datacenter. Best way is to create an image of your VM and copy the generated vhd to a new storage in the secundary datacenter. I like the following approach if you are using ARM:

How to capture a Windows virtual machine in the Resource Manager deployment model

The good thing about resource explorer is that it generates the .json file necessary to recreate the same environment. You can then use it to redeploy the VM in a new region by basically changing a few variables like vhd, storage path and location.

For classic VMs:

Capture an image of an Azure Windows virtual machine created with the classic deployment model