Hoshangabad (Narmadapuram) is a small city with limited options for visitors, but the food is honest and filling. The local staple is dal bafla — the Madhya Pradesh version of Rajasthan's famous dal baati. Wheat dumplings (bafla) are boiled in the Narmada-adjacent tradition, then roasted and dunked in ghee and served with thick lentil dal; it's the kind of meal that sticks to your ribs for hours. Look for it at dhabas along the main highway.
Fresh fish from the Narmada is worth seeking out. Rohu and katla (two common river carp) are typically fried or cooked in a spiced curry and served with flatbread. Several small restaurants near the ghats serve fish dishes at lunch; point and ask what's fresh rather than reading a menu.
The town has a handful of small vegetarian restaurants in the market area serving thali lunches at very modest prices. None are particularly worth seeking out by name — walk the main bazaar, find wherever local office workers are eating, and that will be the right place.