Number + 顿 + 饭
The classifier 顿 (dùn) is used specifically to count meals. It is placed between a number and the word for meal, as in 一顿饭 (one meal) or 三顿饭 (three meals). This classifier is exclusively used with meals and cannot be applied to other food-related nouns.
我今天只吃了一顿饭,现在饿极了。
wǒ jīntiān zhǐ chī le yī dùn fàn, xiànzài è jí le.
I only had one meal today; I'm starving now.
中国人一般一天吃三顿饭。
Zhōngguó rén yībān yī tiān chī sān dùn fàn.
Chinese people generally eat three meals a day.
昨晚那顿饭是我吃过最好吃的一顿。
Zuówǎn nà dùn fàn shì wǒ chīguò zuì hǎochī de yī dùn.
The dinner last night was the best meal I've ever had.