Crush the cardamom pods using a pestle and mortar or a small bowl and the end of a rolling pin. Discard the husks and crush the seeds as finely as possible.
Reserve¼ teaspoon of the crushed seeds for the decoration and put the remaining seeds in a food processor with the lemon rind and sugar. Process lightly until the sugar is almost powdered. Add the butter, eggs, flour and lemon juice. Blend until soft and creamy, scraping the mixture down from the side of the bowl.
Divide the mixture evenly between paper cupcake cases arranged in a 12-hole cupcake tray. Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 20–25 minutes until just firm to the touch. Transfer to a wire rack to cool.
Make the icing. Beat together the icing sugar and lemon juice in a bowl until combined. Add a dash of yellow food colouring, if using, and a few drops of water or extra lemon juice to make a smooth, spreadable icing. Spread over the cupcakes, then decorate with chopped lemon jellies and sprinkle with the reserved cardamom.