What do they eat in Tehran? Fast food! It's true. I'm here in Iran and only have brief access to a computer so I'm typing as fast as I can but they do eat a lot of fast food here. Tehran is a very westernized city except that us ladies all have to wear headscarves. Pizza and burgers are popular here.
In the countryside, the food is probably more ethnic, lots of lamb kebabs and yogurt. But here in Tehran, you would be surprised. KFC is now "Kabooky Fried Chicken" but even despite the sanctions, Coca-Cola is ever-present.