Heat half the oil in a heavy 4-quart pot over medium-high. Add half the sliced shallots and fry, stirring often, until deeply browned and crisp -- 4 to 6 minutes. Lift them out with a slotted spoon onto a paper towel and salt them lightly. These are the garnish.
Reduce the heat to medium. Add the remaining oil and remaining shallots to the same pot. Cook, stirring, until soft and translucent -- 3 to 4 minutes.
Stir in the garlic, ginger, tomato paste, curry powder, turmeric, and red pepper flakes. Cook, stirring constantly, for 60 seconds -- the spices should bloom and the kitchen should suddenly smell good.
Add the rinsed lentils, coconut milk, stock, and salt. Bring to a boil, then reduce to a gentle simmer. Cook uncovered, stirring occasionally, until the lentils have collapsed and the soup is creamy -- 15 to 20 minutes.
For a smoother texture, blend half the soup with an immersion blender and stir it back in. For chunkier soup, skip this step.
Take the pot off the heat. Stir in the lime juice. Taste and adjust salt and lime -- it should be bright enough to wake you up.
Ladle into bowls. Pile the crispy shallots and cilantro on top. Serve immediately.
Source: Our weeknight version. Loosely owes a debt to dal makhani and Sri Lankan mulligatawny without claiming to be either.
We use this when the day ran long and the only thing standing between us and dinner is whatever’s in the dry-goods cabinet. Half an hour, one pot, and a finishing flourish of crispy shallots that does a disproportionate amount of work for how easy it is.