I spoke with a corporation over the phone, and now I want to create something even better

Thus, one of my friends wanted to check out some restaurant software. asked for some, knowing that I have a degree in computer science. I gave him some, and he said he liked one.
I made an appointment to speak with them, explaining that I am the restaurant’s owner (my friend advised me to inform them of this). After seeing their offering, I felt that I could create something even better.
I wonder if this is morally right. Would they come after me saying you stole our concept and joined a call with us if this gets huge one day?

You should not be concerned unless: a) you signed an NDA; and b) they shared material with you that was expressly marked as proprietary and private and that was not specifically excluded by the NDA’s language (which typically leaves out information that is widely known and independently developed).
While trademarked names, copyrighted features, and secret code would be protectable, the “idea” of improving restaurant SaaS is surely not.
Actually, nothing stops you from competing with these individuals in the sales process by referring to your product as “better [other product name]” in an informal, non-written manner.

Why is the qualification “informally, not in writing” relevant, I wonder? There are startups that I can absolutely think of that have stated things like “AI alternative to X,” but perhaps that’s not the case?

Is this really the direction you want to go, or are you just acting on a whim because you think you can do better than them? It’s simple to get carried away with the thrill of believing you can do better, but creating and maintaining anything of this caliber requires much more than simply an idea.

Enhancing an established concept does not violate ethics. Simply avoid using their sensitive information or proprietary code.
It is important to keep in mind that restaurants are difficult to market to; they dislike being pitched to.

Software for the restaurant industry could only be created by an idiot. It’s common knowledge that the restaurant business is the hardest to market to since owners don’t want to waste their time talking to salespeople. They put in 100 hours a week at work and never answer emails or sales calls. They have heard about your QR code menu software and are intrigued.

Whoa, so you’re suggesting that perhaps they ought to take into account goods that could allow them to work less than 100 hours a week?

Go ahead and create a software as a service (SaaS) that addresses disgruntled customers, unsatisfactory staff, and delayed vendors.

Everything is more difficult to produce at scale, despite the fact that you could merely construct your friend the basic tool he needs and put it out of your mind.