Most restaurants will buy from a distributor in a time limited contract. Where a product like beef will be purchased at a set amount for a certain time. Larger chains might buy beef for a year to lock in a cheaper price if they think inflation is going to climb. Also note that restaurants are in competition with eachother so they might not want to be the first to mark up prices.

So the result is that in the event where everything becomes dramatically more expensive in a short time, you will probably see some lag before it shows, but it depends.