Halve the pineapple slices and put into a blender jar. Add mango puree. Squeeze the juice of 1 lemon into the jar. Add sugar and blend till smooth.
Spread salt in a plate. Halve the remaining lemon and rub 1 half along the rims of stemmed glasses. Dip them in the salt. Add ice cubes to the jar and blend again.
Pour the mixture into the prepared glasses and serve chilled immediately.