The first thing is to figure out why it warped. Is this a new table or an old table? Was the top flat to begin with? Does the top and bottom both have finish? It may be possible to fix the top you have, but even if a new top is made it is a good idea to know what happened to this one so it doesn't happen again.
I was able to correct an oak top that warped severely due to a design flaw. Weight (pressure) and time, did it slowly, and it turned out ok.
Before you do anything, take Randy's advice and figure out the cause. No need to do it again! Good luck.