For the blackberry-pineapple jam, sort the blackberries. Then peel the pineapple, removing the “eyes”. Finely dice the flesh, mix the berries and pineapple in a glass bowl and sprinkle with the preserving sugar. Cover and let stand in a cool place for 24 hours.
Then place the mixture in a saucepan and bring to a bubbling boil for four minutes. Remove the pot from the heat and stir in the Campari. Immediately pour the blackberry-pineapple jam into jars, seal tightly and let stand on the lid for 5 minutes. Then invert.