Preheat the oven to fan 160C/180C/gas 4. Using a little butter, grease and line a 20cm round cake tin, about 5cm deep or a rectangular traybake tin 12" by 9"
Remove the stalks from the cherries, carefully slice each cherry in half and remove the stone. Keep the cherries to one side.
Make the crumble topping by sifting the flour into a large bowl. Add the butter and icing sugar or confectioners’ sugar. Using your fingers, rub the butter into the flour and sugar to make a crumb-like mixture, then set it to one side while you make the cake batter.
Whisk the butter and sugar together until pale and creamy (around five minutes using a stand mixer or a whisk), add the eggs in, one by one, and continue to mix well. Add the vanilla extract and cardamom drops or crushed cardamom pods, if using. Mix together well again.
Sift in the flour and baking power and using a spoon, carefully stir the mixture until all the flour is incorporated.
Pour the cake batter into your lined baking tin and flatten with the back of a spoon.
Scatter the halved cherries onto the batter and press down gently.
Scatter the prepared crumble mixture over the top of the cherries.
Bake for 55-60 minutes until a skewer pushed into the centre comes out clean.
Leave the crumble cake in the tin to cool and then remove and place onto a wire rack until you are ready to serve.
Before serving, dust with a little extra icing/confectioners’ sugar.
The cake will keep well in a tin for up to two days.