Heat the neutral cooking oil in a large saucepan over medium heat. Add the onion and cook for 4 to 5 minutes, until softened.
Stir in the garlic and curry powder and cook for 30 seconds.
Add the rinsed lentils, diced tomatoes, coconut milk, water or broth, and salt. Stir well.
Bring to a gentle boil, then reduce the heat and simmer uncovered for 18 to 22 minutes, stirring occasionally, until the lentils are soft and the curry is creamy.
Taste and adjust the salt. Serve with rice, flatbread, or simple cooked vegetables.