Cut the pumpkin into cubes and pour into the cauldron. Pour in 1 cup water and boil until soft. Drain and cool. Cut the orange into quarters, cut off the peel, transparent film from each quarter, and remove the seeds. Place the cooled boiled pumpkin and orange pulp into a blender bowl.
Add sugar. (Optionally, you can replace it with honey.) Pour in mineral water without gas (or chilled boiled water) and lemon juice. Whisk the contents of the bowl for 1-2 minutes on a pulsating setting.
Pour the cooked orange pumpkin smoothie into a tall glass, add a straw, and serve.