Is the expression seriously speaking redundant? For example:
[A asks a question]
[B replies with a joke]
[A and B laugh]
B: No, seriously (speaking), I came to visit my mom.
I think writing "No, seriously..." would imply that A is not believing what B is saying (which isn't the case in my example above).
I'm not very sure, though.
I also thought of the expression talking seriously. But I think I'm translating directly from Spanish (hablando enserio).