About 30 minutes before rolling out the dough, fill a dutch oven or heavy bottomed pot with enough neutral oil to cover 2” (5 cm). Place the oil over medium heat and bring to 355 degrees F (180 degrees C).
Place a wire rack over a paper towel lined baking sheet. On a separate baking sheet, cut out 13 4” (10 cm) parchment squares for the donuts.
On a lightly floured surface, roll the dough out to ½” (1.25 cm) in thickness. Brush away any excess flour. Use well floured 3” (7.5 cm) and 1” (2.5 cm) round cutters to cut out as many donuts as possible and place each on a parchment square. Shape the excess dough into a disk, then wrap in plastic wrap and chill for at least 15 minutes before re-rolling and cutting out more donuts.
Cover the donuts and allow to rise for about 30 minutes or until nearly room temperature, but still slightly cool to the touch. When pressed with a finger, the dough will slowly spring back.
Meanwhile, make the cinnamon sugar. In a wide, shallow bowl, combine the sugar and cinnamon. Set aside.
Once proofed, use the parchment squares to gently lower 2-3 donuts into the hot oil. Fry the donuts for 90 seconds on the first side, then flip over and fry for an additional 90 seconds until golden.
Transfer the donuts to the wire rack. Wait a couple minutes for the oil to come back up to 355 degrees F (180 degrees C), then continue frying the donuts.
Once the donuts have cooled just enough to handle, toss them in the cinnamon sugar to coat.