How can I prevent people from pretending to be a business and registering account under their name?

I have a website that allows restaurant owners to register and list their menus. I think I should somehow confirm that a registered account is actually completed by someone associated to the business to prevent some random person from pretending to be a business owner. What is a smooth way to confirm a business? A couple if ideas I have:

• After they register give them a code to post anywhere on their social media. For example, they comment the code "8dsGDFG9231" on one of their old Facebook posts. As long as they link me to the post, I can confirm their business registration. I am going to assume if someone has access to a business social media, the business registration on my site must be legitimate.

• I can manually call the business number. This might scare some businesses away though.

Is there an obvious better solution to confirm a business account on my website?