Three, or two in a short form. The common mistake is the spelling: the letters aura look like they should be said aw, as in res-tor-ant or res-taw-rant. They are not. The middle is a very short uh, or it disappears: RES-trahnt.
The word came into English from French restaurant, a form of the verb restaurer, to restore. The first restaurants served a strong soup meant to restore a tired person, and that is how the name began.
The ending is ant, which in American English is the ah of father plus nt, and in British English the short o of hot. Put all the weight on RES and say the rest lightly.