Cupcake or Not?

The Aquarium wasn't the only place I found cupcakes on my trip up the California coast. We stopped in a little town called Cambria. I found a bakery called Linn's Easy As Pie Cafe (review to come later). While waiting to get pie, I spotted these "Black Bottom Cupcakes." I'm not sure I would call these cupcakes, as they just looked like muffins with some chocolate glaze drizzled on top. What makes a cupcake a cupcake?