Heat oven to 375°F.
Mix flour, baking powder, salt, lemon rind, and cardamom (1 tsp for subtle flavour, the full 2 tsp if you love it) in a bowl, then cut in the butter. Rub together until it resembles coarse meal. Stir in 1 cup sugar.
Break the eggs into a bowl, and add 4 tsp milk. Whisk together and add to the flour-butter mixture.
Knead lightly into a firm ball, and use your hands to shape this into a log. Cut into 12 equal pieces.
Place each piece on a parchmentlined baking sheet, several inches apart to allow room for spreading, and flatten to a disc.
With your thumb, make a depression in each disc. Fill with a dollop of jam, then pinch the edges together to enclose the jam. Gently flatten again—as far as the jamminess will allow you to. Brush with the other 1 Tbsp milk, and sprinkle with the remaining 1 Tbsp sugar.
Bake for about 12 to 15 minutes, and let cool before eating because the jam will be scary-hot when just out of the oven.