A good alternative to the many fast food restaurants in the Central Station is this former 1st class passengers restaurant.
The place retains much of the atmosphere of the old days. Waiters walk around in traditional black and white outfit and the menu shows traditional French / Dutch items.
You can either have a quick lunch/diner or drink in the cafe or take some more time and sit down in the restaurant area.
A good alternative to the other restaurants in the station before you catch your train out of Amsterdam.