Recover from AWS RDS cross-region DR

Question

I had a RDS in one region (us-east-1) and it's read-replica in another region (us-east-2). But due to some reason, the source DB is deleted and now the read-replica which is in another region (us-east-2) is promoted. I know I can't create the read-replica again of DB in us-east-2 back in us-east-1 since it needs source DB. I wanted to ask, how do I make the RDS in us-east-1 primary again? I can't seem to find anything regarding it?

I want things to go back to the previous state i.e. Primary DB in us-east-1 and DR read-replica in us-east-2.

REF: https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_ReadRepl.XRgn.html