Lumbini is not a foodie destination. The Tourism Village has a small cluster of mid-range hotel restaurants serving identikit menus of Indian, Tibetan, and Continental food at inflated prices — passable, never memorable. Nepali momos and dal bhat at the simpler restaurants near the main gate are usually the best value.
Several monasteries — notably the Korean and the Japanese — run vegetarian canteens that welcome visitors at lunchtime. The food is simple, monastic, and excellent. A small donation is expected.
The market town of Bhairahawa, 20 minutes away, has a wider range of restaurants serving North Indian and Nepali food at local prices.