Is this sentence a question or a metaquestion?

It’s both. It has the form and function of a question, so it is a question, but it is about the questioning process, so it is also a metaquestion. Formal languages such as first or second order logic have paradox-avoiding restrictions that force an either/or choice between using regular langauge or meta langauge, but not both, but English, being a natural language, has no such constraints.