Rinse and peel rhubarb, cut into small pieces.
Butter casserole dish and line with diagonally cut bread slices. Place rhubarb on top. Combine cream with eggs, cinnamon and vanilla sugar, pour over bread slices. Bake in preheated oven at 180°C (approximately 350°F) for about 25 minites or until golden brown.
Sprinkle with powdered sugar and serve.