Divide the dough into three equal portions.
Take one of the portions and roll it out with a rolling pin until it is flat, about 1/4 inch (1/2 cm) thick.
Sprinkle a bit of raisin down the center of each piece, then fold the dough over and roll it into about 15-inch rope, pinch the ends tightly. Repeat with the remaining dough pieces.
Gather the ropes and squeeze them together at the very top. Braid the ropes together like braiding hair and squeeze the ends together when complete.
Line a baking sheet with parchment paper and place the Challah on it.
Place the pan somewhere warm, cover with a towel, and let it rise until puffed, about an hour.
Heat the oven to 400°F/200°C. When ready to bake, whisk the egg with a tablespoon of water and brush it all over the Challah.
Sprinkle sugar and cinnamon.
Slide the Challah on its baking sheet into the oven and bake for 25 to 30 minutes. The Challah is done when it is a rich golden brown and registers 190°F/90°C in the very middle with an instant-read thermometer.
Let the Challah cool on a cooling rack. Enjoy!