The small cafes around the central square and main street serve standard Tunisian food: couscous with lamb or chicken, merguez sausages, brik (thin pastry filled with egg and tuna, fried until crisp), chopped salads, and bread. Harissa — the hot red chilli paste that appears on virtually every Tunisian table — will be on the side. Prices are low.
These are places that cater to local workers and passing Tunisian travellers rather than tourists, which means the food is honest and there is no tourist markup. The atmosphere is functional rather than charming. The cafe closest to the central square is usually the easiest to find and the most likely to be open.