In a large pan, add oil, onion, salt and pepper. Cook over medium heat, stirring often, until onions are translucent, about 5 to 7 minutes.
Add other seasonings in the ingredients list, stir and cook for 3 minutes.
Add lentils, tomato sauce, and coconut milk, stir well. Bring to a boil then immediately lower heat to a very low simmer (lightly bubbling) and cover with a lid.
Cook the lentils (covered with a lid) for 25 minutes, stirring every so often.
Cook another 15 to 20 minutes while watching for the liquid level, still covered. You may want to add approximately 1/2 to 1 cup vegetable broth or water during this part of the cooking process. You want the lentils to be soft yet not mushy.
Serve with cilantro or other fresh herbs as desired, and optional red chili flakes.