Heat the oil in a large pot over medium heat until shimmering and fragrant.
Add the chopped onion and cook, stirring often, until translucent and soft—about 5 minutes. The onions should turn a light golden color and smell sweet and inviting.
Stir in the minced garlic and grated ginger, cooking for another minute until fragrant, filling your kitchen with a spicy, fresh aroma.
Add the ground cumin, coriander, turmeric, and chili powder. Toast the spices for 30 seconds, until aromatic and slightly darker, which helps unlock their full flavor.
Pour in the vegetable broth and bring the mixture to a gentle boil, stirring to combine all the flavors evenly.
Add the rinsed red lentils to the boiling broth. Stir once, then reduce the heat to a simmer, keeping the pot partially covered.
Let the lentils cook gently for about 20 minutes, stirring occasionally. You'll see them soften and start to break down, turning the sauce velvety and thickening the curry.
Check the lentils—they should be tender and falling apart slightly. The sauce should coat the back of a spoon with a rich, warm hue.
Stir in the coconut milk and season with salt to taste. Allow the curry to simmer for another 5 minutes, which helps meld the flavors and add creaminess.
Turn off the heat and let the curry rest for a few minutes. This enhances the depth of flavor and thickens the sauce further.
Serve hot over cooked rice or with warm bread, garnished with chopped cilantro if desired. Enjoy the comforting, earthy flavors of this simple red lentil curry.