So like the person above said. However the first example "You are asked (by person A) to write a letter. What did you write?" is incorrect as it is in the past tense. If someone says "you are asked" then it is talking about past continuous in other words it is talking about something that started in the past that is still being done in the present. E.g. "You are asked to clean the plates. What do you do?" in this sentence you have already been asked to clean the plates in the past, but it requires a action performed in the present.

Hi, Hunter Basically "you are asked" is present tense and "you have been asked" is past tense. If someone says: "You are asked...", it's usually a question asked by someone who is just repeating what someone else said. For example: "You are asked (by person A) to write a letter. What did you write?", asks person B. "You have been asked" will be used to form a tag sentence: "You have been asked to write a letter before, haven't you?" Hope this makes sense ;)