Slice the leaves off the pineapple and halve it. Wrap 1 half and store in the fridge (see our tip below). Slice the skin off the remaining half, scooping out any tough ‘eyes’ left behind. Roughly chop the flesh, discarding any woody bits of core. Pop the chopped pineapple into your blender.
Tuck the baby leaf spinach into the blender and spoon in the yogurt.
Measure out 1 tsp cumin seeds and scatter them into a dry frying pan. Toast for 2 mins, tossing regularly, till the seeds smell nutty. Tip them into the blender. Add a small pinch of salt.
Add a few ice cubes and pour in 150ml cold water. Blitz for a few mins till smooth, then pour into glasses and serve.