' The American writer of non-fiction and fiction, Rodney William Whitaker (1931–2005), is best known for some novels that he wrote under the mononym pen name, "Trevanian." '
I've seen other examples, but this seems to be the most recent one (he died 4 years ago...). It's not a very common practice, but I'm sure you can do it. Thanks for asking the question; I hadn't even considered it, but if I ever do get published I'd want a penname, and a mononym, in my opinion, looks better on paper than some names.
Good luck on writing your book and getting published!