Cream together butter, sugar, vanilla extract, and salt until fluffy.
Gradually beat in the eggs.
Whisk together the flour and baking powder. Add to the butter-sugar-egg mixture. Gradually stir in the milk and check that the batter has the right consistency. It should fall heavily from the spoon.
Use a silicone spatula to briefly fold in the poppy seeds, so that patterns form in the batter. Pour the batter into a baking pan lined with parchment paper. Evenly spread the sour cherries on top and bake for 50-60 minutes.
Let the cake cool before removing it from the pan, and dust with powdered sugar.