Saute the onion, garlic and ginger with the olive oil (or water/broth if you wish to avoid oil) over medium high heat for 3-5 minutes, until onion is soft.
Add the curry powder to the pan along with the coconut milk, water, sweet potatoes and red lentils. Stir to combine everything.
Lower the heat to medium and allow the lentils to simmer, covered, for 50 minutes. You will want to stir occasionally, especially near the end of the cook time, to keep the lentils from cooking to the bottom of the pan. The sweet potatoes and lentils should both be soft and well cooked.
Add salt at the end, adjusting amount based on your taste.
For the Turmeric Rice
Combine the rice, water, turmeric and pepper in a sauce pan. Bring to a boil. Reduce heat to medium and allow the rice to simmer, covered, for 15 minutes.
Remove pan from heat. Keep covered for 10 minutes.