Prep your ingredients: Rinse the red lentils under cold water until it runs clear.
Chop the onion, mince the garlic, and grate the ginger. If using extra veggies, chop them now.
Sauté the aromatics: Heat the oil in a large pot over medium heat. Add the onion and a pinch of salt.
Cook 5–7 minutes, stirring occasionally, until soft and lightly golden.
Add garlic and ginger: Stir in the garlic and ginger. Cook 30–60 seconds until fragrant, being careful not to burn.
Bloom the spices: Add curry paste (or curry powder), turmeric, cumin, coriander (if using), and chili flakes. Stir for 30 seconds so the spices release their oils and deepen in flavor.
Build the base: Pour in the diced tomatoes and stir, scraping the bottom of the pot to lift any browned bits.
Simmer the lentils: Add the rinsed lentils and 2 cups of broth.
Bring to a gentle boil, then reduce to a simmer. Cover partially and cook 10 minutes, stirring now and then.
Add coconut milk: Pour in the coconut milk and stir. Continue simmering 8–12 minutes, until the lentils are tender and the curry is thick and creamy.
Add more broth if it gets too thick or sticks.
Season and brighten: Stir in 1 teaspoon salt, black pepper, and the lime juice. Taste and adjust salt, acid, and heat. If using spinach or other quick-cooking greens, fold them in now until wilted.
Serve: Spoon over hot rice or serve with warm naan.
Garnish with fresh cilantro and an extra squeeze of lime if you like.