Boil the potatoes in their skins until not too soft, rinse with cold water and cut into 1.5 cm cubes.
Peel the onions and cut into half rings. Cut the bell bell pepper into 1.5 cm pieces.
Heat oil in a large frying pan. When oil is very hot, add turmeric, potatoes, peppers and onions. Salt and roast, turning, for 3-4 minutes.
Drizzle water over the top, lower the heat and saute with the lid on for about 10 minutes until the peppers are soft.
Remove lid and roast, stirring, until all liquid has evaporated.
Season the turmeric potatoes with salt and pepper.