Do you mean what is your staple food? If so ，我吃米饭，米饭是中国南方人的主食。

I don't get the question. In Chinese we don't say '你吃什么'。 What did you eat before, 你之前吃了什么。 What do you want to eat, 你想要/打算要吃什么。 What do you prefer to eat normally, 你通常喜欢吃什么？ 你吃什么 is more like 'what kind of food you live off'.

我什么都吃，一般中午吃米饭，早上和晚上吃面食。