Heat oil in a large pan or wok over medium-high heat.
When the oil is hot and begins to ripple, add onion, salt, garam masala (or tandoori spice mix), red chili flakes, and cayenne. Sauté 3-4 minutes, until the spices are fragrant and the onions are translucent.
Add garlic, sauté 1-2 minutes.
Add tomatoes, and simmer another 4-5 minutes. Add lentils and water. Bring to a boil, then cover pan and reduce heat to medium-low.
Simmer until most (but not all) of the water has absorbed and the lentils soften, about 20 minutes. Add turmeric. Taste and add extra salt if desired.Serve dal warm, alone or with rice.
Leftovers:Store leftovers in the fridge, and use within 3-4 days.Make Ahead and Freeze:Let lentils cool to room temperature, and freeze for up to 6 months.
Notes
Serves 4 as main dish, 8 as side dishTo Substitute Homemade Tandoori Spice Mix: Blend 2 TB cumin, 2 TB garlic powder, 2 TB paprika, 4 tsp ginger, 1 TB coriander, 2 tsp cardamom, and use 2 TB of mixture in place of pre-made spice mixRecipe Adaptions:
Change the spice: Substitute berbere (an African spice blend) for garam masala or tandoori masala
Make it less spicy: Omit the cayenne and/or red pepper flakes
Make this dal heartier: Add 4-5 diced Yukon Gold potatoes to the pan when you add the lentils
Turn this dal into soup: Add 4-5 diced Yukon Gold potatoes to the pan when you add the lentils. Add 4 cups of water instead of 3 cups. Add 2 or 3 large handfuls of fresh spinach to the dal about 5 minutes before the lentils are done cooking.
(NOT VEGAN) Add eggs: Crack 2 - 4 eggs into the lentils about 4-5 minutes before they're done cooking. Keep the pan covered.