Add the washed lentils to an appropriate lidded pot over medium heat until cooked. Finely chop the onion. Heat some oil into a large pan, then add onion and turn the heat down to medium-low. Cook them slowly until golden.
Finely mince garlic and add to the pan, followed by spices (turmeric, cumin, coriander, and chili). Fry until fragrant, then add tomato paste and cook until it has lost its raw taste.
Add the cooked lentil with some water to the pan and stir to combined. Cover with lid and cook over low heat for about 20-30 min, until seems cooked. Adjust the seasoning to taste. Add the lemon juice just when the stew is nearly done and you are ready to turn off the heat and serve.
Serve the daal stew with cooked rice. Garnish with some yogurt and cilantro if desired. An onion-tomatoey salad as a side is seriously advised...