Build the Aromatic Base : In a 5-quart Dutch oven, heat the avocado oil over medium heat. Add the chopped onions and cook, stirring frequently, for 7 to 9 minutes, until they have softened and become translucent. Stir in the minced garlic and grated ginger, continuing to cook for another 2 minutes until fragrant.
Bloom the Spices : Add the black mustard seeds, ground turmeric, smoked paprika, ground coriander, garam masala, and cayenne pepper directly to the pot with the aromatics. Stir constantly for 60 seconds to toast the spices and unlock their full flavor.
Create the Tomato Foundation : Pour in the chopped Roma tomatoes and the fine sea salt. Stir everything together, scraping up any browned bits from the bottom of the pot. Allow this mixture to cook for about 5 minutes, letting the tomatoes break down and form a thick, fragrant paste.
Combine and Simmer : Add the rinsed red lentils, the low-sodium vegetable broth, and 4 cups of water to the pot. Stir well to combine. Increase the heat to bring the liquid to a steady simmer, then reduce the heat to low, cover the pot, and let it cook for 25 to 35 minutes. The additional liquid helps create a wonderfully creamy, scoopable dal.
Final Touches : Uncover the pot and stir the dal. The lentils should be completely soft, and the mixture should have thickened into a stew-like consistency. If it's too thick for your preference, you can stir in another splash of hot water.
Garnish and Serve : Ladle the warm dal into bowls. Top generously with fresh, chopped cilantro and serve immediately with fresh lime wedges on the side for squeezing over.