Cook the Lentils: Place the red lentils, salt, turmeric, a 2-inch piece of ginger, cardamom pods, dried chile (or chile flakes), and 6 cups of water in a medium pot. Bring the mixture to a boil over medium-high heat, then lower the heat to a simmer. Cook, stirring occasionally, until the lentils are tender and the mixture has thickened to a creamy consistency, about 30 minutes.
Prepare the Brown Butter: Chop the remaining 1 ½-inch piece of ginger finely. In a large skillet, melt the butter over medium heat. Allow it to cook until it stops foaming and turns a deep golden-brown color, approximately 5 minutes. You’ll know it’s ready when the bubbling sound lessens, and the butter smells rich and nutty.
Infuse the Spices: Add the cumin seeds to the browned butter and toast them for about 30 seconds. Stir in the sliced shallots and chopped jalapeños, and cook, stirring occasionally, until the shallots are deeply caramelized and browned, which will take 7-10 minutes. Next, add the chopped ginger, garlic, and garam masala, and cook for an additional 30 seconds to release their aromas.
Combine and Finish: If the dhal is too thick, add a bit of water to adjust the consistency to your preference. Remove the cardamom pods, the large piece of ginger, and the dried chile before serving. Divide the dhal into bowls, spoon the spiced brown butter mixture on top, and finish with a dollop of yogurt and a sprinkle of flaky sea salt. Garnish with fresh cilantro leaves if desired.