When doing your market research (by which I specifically mean talking with your target market about their pain - you can't do market research in your basement, only competitor research which is not the same thing) ask them about sales reps for their other providers that they like and trust. Get an introduction wherever possible.

1) If nothing else, people who already sell to restaurants understand the market and can introduce you to other owners you can speak with, and

2) You probably want a salesperson with industry expertise and existing relationships, rather than someone with App / SaaS experience. Even if they've previously sold produce or tableware or linen services, you can teach them the technical basics and they can sell it in terms that will create cutthrough in the market.

Lastly, when people Ask HN about finding a technical co-founder, the advice is nearly unanimous: try learning some of the skills yourself. The same is true of Sales and Business strategy - you may never become an expert, but forcing yourself to learn the basics will help you identify the really good operators in that space.

Good luck!