Wash the sweet potato and then slice into 1 cm width rounds. Place in a bowl with water and soak for 5 minutes. Drain water.
Place the potatoes in a pan making sure not to overlap them. Add water, sugar, lemon juice and salt. Cover with a otoshibuta. Bring to a boil and then reduce heat to low. Simmer for 15-20 minutes or until you can pierce a toothpick through.
Remove from heat and allow it to cool. Serve and enjoy!