Who is the author of "To Kill a Mockingbird" described as Dill?

I assume you mean, "Which author is described in To Kill a Mockingbird as Dill?" In other words, what author is the character of Dill based on.

Given that as the question, the answer is Truman Capote.  Truman Capote spent his summers with his aunts, who were neighbors of Harper Lee.  Harper Lee based her character, Dill, on the fragile and rather odd (even at that age) Capote.