How to find a cars owner?

You don't. Police or insurance can under some circumstances, and towing companies with actually possession, but you can't.

Federal law prohibits release of that information to you.

18 U.S. Code § 2721 - Prohibition on release and use of certain personal information from State motor vehicle records.

Full text is here if you care to read it. https://www.law.cornell.edu/uscode/text/18/2721

I believe if you sign up for Car-Fax, you can get that information. Or if you have a friend in law enforcement, he might help you out.

If vehicle was involved in a hit & run in which you were the victim you can pass it on to the police, otherwise that information is confidential.

Such information would only be privy to the department of motor vehicles and law enforcement.

Need to find a crooked cop to illegally run it for you.

Nope, unless your not-so-smart uncle works for the police department.

if you know someone who can access dmv records, they can help. if not, you probably are not going to find out who the r.o. is.