Warm the pot: Heat the olive oil in a large pot or Dutch oven over medium heat.
Sauté the aromatics: Add onion, carrots, and celery with a pinch of salt.
Cook 5–7 minutes until softened and lightly golden. Stir in the garlic and cook 30 seconds until fragrant.
Bloom the spices: Add cumin, coriander, paprika, turmeric, and red pepper flakes. Stir for 30–60 seconds to toast the spices.
Add lentils and tomatoes: Stir in the rinsed lentils and the can of diced tomatoes with their juices.
Pour in broth: Add the broth and bay leaf.
Bring to a gentle boil, then reduce to a simmer.
Simmer until tender: Cook uncovered, stirring occasionally, until lentils are soft. About 20–25 minutes for red lentils (they’ll break down), or 30–40 minutes for brown/green lentils (they’ll stay more intact).
Season and adjust texture: Remove the bay leaf. Add 1 teaspoon salt and a few grinds of black pepper, then taste.
If you want a creamier texture, mash a ladleful of soup against the side of the pot or blend briefly with an immersion blender.
Add greens: Stir in spinach, kale, or chard and cook 2–3 minutes until wilted and tender.
Brighten it up: Stir in lemon zest and juice to taste. Start with half the lemon and add more if you like a brighter finish.
Finish with herbs and olive oil: Turn off the heat and fold in parsley or cilantro. Drizzle with a little olive oil for richness.
Serve: Ladle into bowls and top with crumbled feta or a dollop of yogurt if you want extra creaminess.
Add warm bread on the side.