Place the dough on a lightly floured surface. Add two tablespoons of flour to the dough, then knead until smooth, about three minutes, adding more flour if necessary. Divide the dough into eight parts. Shape each into a ball. Return the dough balls to the bowl, and cover with a dry cloth; let rest 20 minutes. In a small bowl, mix the remaining 1/2 cup sugar and the cinnamon; set aside.
Preheat the oven to 200°. In a 10-inch skillet, add 1 inch of oil and heat over a high flame to 360°. Place one ball of dough on a lightly floured surface; press it into a flat circle. With a lightly floured rolling pin, roll out the dough into a 6-inch circle. Stretch it to make it as thin as possible. Transfer to lightly floured waxed paper. Repeat with the remaining dough.
Cook about 1 1/2 minutes in the hot oil, or until the underside is golden. With tongs, flip the buñuelo; cook the other side until golden. Transfer to a pan lined with paper towels. Sprinkle both sides with 1 tablespoon of the cinnamon-sugar mixture; keep warm in the oven. Repeat with the remaining dough and cinnamon-sugar.