Rinse the red beans thoroughly and soak them in plenty of water for at least 6 hours.
Place the soaked red beans in a pot, add enough water, and bring to a boil.
Once it starts boiling, discard the first water, pour in fresh water, and cook until the beans are tender.
Drain the cooked beans in a sieve and mash them finely.
Transfer the mashed beans back to the pot, add sugar and salt, then simmer over medium heat while stirring.
When the paste thickens, reduce the heat to low and keep stirring until glossy and done.