Preheat the oven to 170 ℃ (convection) or 180℃ (top/bottom heat mode).

Grease the baking tin with butter and dust with flour or e.g. breadcrumbs.

If your pistachios are in their shells, shell them and measure half a cup of shelled nuts.

Mix together flour, cardamom, baking powder and baking soda.

Cream the butter together with sugar and vanilla until fluffy and smooth - I mix for a few minutes at the highest speed of the mixer.

Add eggs one by one to the butter mixture and briefly mix each on low speed of the mixer.

Add wheat flour in portions to the dough, mixing briefly on low speed.

Add flour alternately with buttermilk until you have added all of it to the dough.

Stop mixing when you can still see remnants of flour, then just briefly stir the dough with a spoon.

Transfer the dough to the prepared mold.

Blend the pistachios in a food processor or blender into a fairly fine powder.

Add the remaining crumble ingredients to them and briefly mix them together, or knead with your fingers.

Spread the crumble on top of the dough - there will be a lot of it.

Finally, you can additionally sprinkle the top of the cake with chopped pistachios.

Place the cake pan into a hot oven and bake for about an hour - check with a skewer to see if the cake is well baked inside.

Cool the finished cake before serving.