What you're looking for are called dialog cues. They are, as the name suggests used to give the reader cues on how the dialog is delivered.
In your case I'd borrow one of Margie Lawson's examples (quoting "Blaze of Memory" by Nalini Singh) on the link above and combine it to:
“Why are you here?” Tatiana’s voice was utterly without inflection.
I.e. leave the question mark in place (it is after all a question) and describe the voice after (or before, both usually work as well) the line of dialog.
Update: For completeness, I might add that the idea I get is that while dialog cues might be used often, it will of course be very problematic if it's used for every line of dialog.
I probably use it now and then, for instance when the delivery of the dialog is unusual (and that fact is important to the story), when it might add to a conflict or dramatic situation, and when it carries subtext. (Or at least I try to...)
I learned about dialog cues from Margie Lawson's lecture package, "Empowering Character's Emotions". These lectures cover much more than that (it's a package of 11 lectures) but they do cover dialog cues along with a lot of other components in a text. (She also has one lecture package specifically on dialog cues, but I haven't checked it out yet...)
She does cover dialog cues on her blog though. While some of the examples may be better and some worse, the idea behind dialog cues is solid as long as you make them your own.