This is delicious and quick to make. Use your favourite jam — it looks super with a red jam, too. I like to make two of these with different colour jams and serve a slice of each. You can use a little milk to brush over the pastry if you don’t want to use up an egg yolk, but the yolk will give you a glossier and deeper colour.
Put the butter in a bowl with the flour, sugar, eggs, baking powder and a pinch of salt and mix together well. Knead the dough into a compact ball, flatten a bit and wrap in plastic wrap. Chill in the fridge for half an hour or so.