Rinse the red lentils thoroughly in cold water until the water runs clear, then drain well.
Heat the oil in a large pot over medium heat until shimmering and fragrant.
Add the chopped onion and cook, stirring occasionally, until it becomes translucent and soft, about 5 minutes. You should smell a sweet aroma and see the onion turning a light golden.
Stir in the minced garlic and grated ginger, cooking for about 1 minute until fragrant and slightly bubbling.
Add the toasted cumin seeds (or ground cumin), turmeric, and chili powder. Stir constantly for about 30 seconds until the spices release their aroma and turn a darker, richer color.
Pour in the warm vegetable broth and add the rinsed lentils. Bring the mixture to a gentle boil, listening for a bubbling sound.
Reduce the heat to low, cover the pot with a lid, and let it simmer gently for 20-25 minutes. Stir occasionally to prevent sticking, and watch as the lentils turn soft and start to break down, creating a thick, creamy texture.
Once the lentils are tender and the curry has thickened, stir in the coconut milk and cook uncovered for another 2-3 minutes to meld the flavors and increase creaminess.
Turn off the heat, squeeze in fresh lemon juice, and stir well to brighten the flavors. Taste and adjust salt or spice if needed.
Garnish with chopped cilantro just before serving for a fresh, herbal note.
Serve the hot, creamy curry with rice, naan, or your favorite bread, and enjoy the comforting flavors and textures.