Pour freshly squeezed grapefruit juice through a sieve. Wash the lemon hot and peel the peel thinly. Squeeze the lemon. Put the grapefruit and lemon juice, lemon peel, cassis liqueur, cinnamon and steranis in a pot.
Stir in jam sugar. Wash the carambola, dab dry and cut into thin slices. Cook everything together for 4 minutes until bubbly. Remove lemon zest, cinnamon and star anise. Pour the jelly into prepared glasses and place the carambola slices on the sides of the glass - or, as soon as it gets a little firm, on the jelly surface.
Results in about 4-5 glasses (300 ml each).