Why once a day? When they are outside they graze and eat all they want.I would offer him once a day a little more than he can eat and some do a second smaller portion in the evening.
@Aaron23 the slow grow, low food amount sounds like you have been reading/getting outdated info. Most books and people proposed that along with other methods that have since been proven incorrect. If you haven't had a chance, please take the time to read through the posts "pinned" to the top of the species specific section for African - Sulcata tortoises. Especially starting with "How to Raise a Healthy Sulcata or Leopard" http://www.tortoiseforum.org/threads/how-to-raise-a-healthy-sulcata-or-leopard-version-2-0.79895/