Ideally you shouldn't be using the browser as a transport mechanism. The browser should only be a means of data entry - redirect the user to the payment processor so they can enter their details, but then the redirect back should just go to a "payment status" page while your system on the backend waits for a notification (webhook, etc) from the processor in the background which would then update the record on your side (at which point the read-only status page will pick it up on its next poll and then redirect the user to the next step of whatever process they were doing).

This also allows you to recover the flow should the user drop off after they've paid - you can email them a link to that "payment status" page so they can "rescue" the flow without having to start from scratch.