Hello, @Das, Riyan !
Edit: I've had this verified by a couple experts in this area so I'm going to move this to an answer for additional visibility. If you have any questions about ExpressRoute or site-to-site VPNs, feel free to start a new thread and we'd be happy to work with you!
How do I connect to a on prem SAP system and run an RFC function from an Azure VM?
Similar to what @JimmySalian-2011 suggested, the recommendation I received was to use a means to connect on-premises users and systems to Azure with either site-to-site VPN or express routes. With that, if the on-prem system is reachable by the Azure web app, RFC connection should be possible provided that networking firewall allows the connection.