Place pre-sifted flour mixed with baking powder, vanilla and sugar in a large bowl. Add chopped butter as shown. Mix in the eggs and knead into a smooth dough. I like kneading the dough with hands. Form a ball, flatten it lightly and wrap it in foil or place in a bag. Place the dough in the refrigerator for at least 30 minutes.
Wash plums while the dough is cooling. You can use any plums. I used the mini sugar plums. Remove pits and cut them into small pieces.
After about 30 minutes, remove the dough from the refrigerator. Divide into two equal parts. Roll out one part of the dough and place in the bottom of the pan. I used a glass pan size 22 x 32 cm.
Place pieces of plums on the dough. Top the plums with the rest of the dough. Roll piece by piece, slightly flatten and lay dough pieces side by side. Finally, lightly tap everything. The dough is super flaky and you may not be able to roll it out perfectly.
Place the the cake in a 320 degrees F, preheated oven and bake for about 50 minutes, until the crust is lightly browned on top. When done, remove from the oven and let it cool completely before cutting. Store in the refrigerator.