sorry, I didn't take note
According to their website -- for brunch and dinner Sundays
Yes, I have seen people dine there on Sundays. I am not sure of there are any seasonal limitations - you may want to call them just in case. It is always good to make reservations. I would not advise to go there on Sunday without making sure there will be a spot.
Get quick answers from the Flying Chestnut staff and past visitors.