Method

1. Sift through lentils to ensure there are no small stones, then rinse under running water, until water runs clear. Soak lentils in enough water to cover them, and set aside for up to an hour.
2. In a large pot, heat canola oil over medium heat. Add whole cumin seeds, allowing them to sizzle for 20 seconds, until fragrant.
3. Add onion, garlic, and ginger and reduce heat to medium low. Cook for 10-15 minutes, stirring often, until onions begin to brown.
4. Add diced tomatoes, turmeric, pepper, salt, and cayenne (if using). Cook for another 10-15 minutes, stirring often, until tomatoes are broken down and onions are very soft.
5. Strain lentils, rinse once more, and add to pot along with 6 cups (1.5 L) water.
6. Bring to a boil, reduce heat, and simmer for 30-45 minutes (length of time depends on how long lentils were soaked), stirring every few minutes, until lentils soften and daal thickens.
7. Remove from heat, garnish with garam masala and cilantro (if desired), and serve.