For the dough,

Preheat the oven to 190C or 375F.
Butter a 9″ springform cake pan.

In a bowl working with a fork, combine the butter with the sugar until they form a paste. Add the egg and vanilla, mix.

Add the flour with the baking powder and mix until it forms a soft dough.

Using your fingers or a spoon, spread the dough until it covers the entire bottom of the cake pan.

Bake for 20 minutes until golden brown.

For the filling,

While the dough is cooking, dissolve the cornstarch in the cold milk, add the sugar and cinnamon and cook over medium heat, stirring all the time when it starts to thicken. Let it boil for a minute.

Place the raspberries in a layer on top of the baked dough.

Remove the cinnamon stick. Add the custard on top. Spread.

Return to the oven for 20-25 minutes until the surface browns. It’s going to inflate in the oven. It’s normal.

Allow cooling entirely in the oven.
Dust the Kuchen with powdered sugar just before serving. Keep cold.