As your ask is on AKS (Managed service from Azure) with HA enabled Clusters you already have more than one master running. As AKS is a managed offering service you will will not have the visibility/control on this.
Can I get a way to create an AKS with multiple control planes?
For this you can check the AKS Uptime SLA, Uptime SLA guarantees 99.95% availability of the Kubernetes API server endpoint for clusters.
Please check this document for more details.
If you are using AKS Engine (unmanaged service), then you can specify the number of masters. Please refer to this document for more details.
Hope this helps.
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