How to Make Plum Cake?

My Oma's Pflaumenkuchen (Plum Cake) non-yeast easier version
2 1/3 cups all-purpose flour
3 tsp baking powder
1/3 cup granulated sugar
1 tbsp vanilla sugar (or use vanilla Greek yogurt see below)
1/2 cup Greek yogurt (use vanilla if you don't have vanilla sugar)
1/3 cup milk
1/3 cup sunflower or olive oil
Approx 2 lbs of prune plums (Italian plums are best that come out at the end of August usually) pitted and quartered
2 cups all purpose flour
1 cup granulated sugar
1 cup of cold butter (cubed is easier to work with)

Preheat oven to 350°
In a large mixing bowl mix 2 1/3 cups of flour, baking powder, 1/3 cup sugar + 1tbsp (if you can vanilla sugar use) and salt.
Add yogurt, milk and oil using dough hook mix for a minute or so until dough holds together (do not over beat) or you can just mix with wooden spoon and kneed lightly with hands until the dough holds together
Press dough into a greased 9"×13" pan OR divide dough into two 9" springfoam pans
Place plum quarters in rows on top of dough (I do one outer and one inner circular rows then pop one in to fill centre)
If desired for preference of tarte or sweet you can Sprinkle some sugar on top to help cut out the tartness of the plums.
Mix together 2 cups flour, 1 cup sugar and 1 cups butter to make streusel dough. Crumble over top of plums (make sure top and sides are fully covered)
8.Bake 350° for 50-60 minutes or until top is lightly browned
Let cool and serve