The right option is “The food ON your plate” since the food is on its surface. The word “IN” can be used when referring to a bowl or to another similar container.

Native speakers use both. Currently, in printed text, "on" the plate is used about 70% of the time and "in" the plate about 30% of the time. About 150 years ago, "in" was more popular. Here is a Google N-gram showing the frequency of "on the plate" and "in the plate." https://books.google.com/ngrams/graph?content=on+the+plate%2Cin+the+plate&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Con%20the%20plate%3B%2Cc0%3B.t1%3B%2Cin%20the%20plate%3B%2Cc0

Do you put food inside the plate? no. You put it on top of the plate and then eat it.

The food on the plate is better