Halve the pitahaya with a straight cut and scoop out the pulp with a spoon and place in a colander. Now carefully press the pulp through the sieve so that the seeds remain (does not work particularly well).
Put the remaining ingredients together with the seeds in a saucepan and briefly bring to the boil. Then pour the liquid into the pitahaya bowls and place in the refrigerator. Stir every now and then with a spoon so that the kernels are well distributed.
After cooling, carefully cut the pitahaya halves in half with a knife and serve with a spoon.