1. Preheat the oven to 350°F (175°C). Line a springform tin (10 inches/26cm) with baking parchment and set aside.

2. Mix flour, xylitol, and baking powder in a large bowl. Add the butter in small pieces and rub a little between your fingers together with the flour to get even smaller pieces. Add the egg and vanilla extract and mix everything until you get streusels – make sure all the flour is incorporated and nothing is left on the bottom of the bowl. Pour the streusels into the prepared baking tin and press to the bottom and sides to create a nice crust – make sure the sides are about 0.8 inches/2cm high. Set aside until needed.

3. For the filling, mix the xylitol with the cornstarch in a bowl, then add the eggs and mix everything well – there should be no lumps of starch left. Add the sour cream, crème fraîche, heavy cream, and vanilla extract to the bowl and mix well. Pour the mixture into the prepared baking tin, shake it a bit to allow air bubbles to come up, and then bake for about 50-60 minutes. The cake is ready when the filling is firm around the edges and has a bit of color with a center that is still wiggly if you move the baking tin. Take out of the oven and sprinkle immediately with the xylitol-cinnamon mixture and then let cool completely.