$
Budget
Street stalls are everywhere, but a nice place to go is Nlongkak round about. Here there's a bit of a variety, and plenty of places to get a beer. A plate of beans should cost between 200-500CFA, an omlet around 500 or 1000 if in a resturant with chips, and a plate of spagetti maybe 500CFA. Prices may vary considerably depending on the honesty of your vendor.
Top end
$$$
Cafe Yaoundé
Hippodrome
Pricey 3000-7000 ish food. Seems to be catering to the expat crowd with a focus on European style cuisine. Nice ambiance with patio seating in a lush garden area. One of the best restaurants in Yaounde