Put oven rack in middle position and preheat oven to 500°F.
Melt butter in a 17- by 12-inch shallow baking pan in oven, about 2 minutes. Spread tortillas, in baking pan, overlapping slightly and turning each over once to coat with butter.
Stir together sugar, cinnamon, and a pinch of salt. Sprinkle evenly over tortillas.
Bake tortillas until golden and puffed in spots, 4 to 5 minutes.
