Lemon-flavored lemonade

I like Charley's cheesesteaks, and I like their lemonade, but ordering is always a linguistic challenge for me.
"[Blahblahblah]...and a medium lemonade, please."
"Ok, which flavor lemonade? We have peach, blueberry, and strawberry."
"Uh... the ... lemon flavored one?"

That last line comes with a question mark because that's me internally wondering if a.) that comes across as condescending, or b.) I'm somehow out of touch with modern lemonade trends.

Like, how do communicate to someone that you want a "lemon-flavored lemonade" without one or more of you feeling stupid?

After posting this on Facebook, I got the answer -- just say you want an original lemonade.I guess that makes sense.