Heat one tablespoon of olive oil in the large pot over medium heat, until it shimmers and begins to ripple.
Add the diced onion and cook, stirring occasionally, until translucent and slightly golden around the edges, about 5 minutes. You’ll notice a sweet aroma filling the air.
Stir in the minced garlic and toast for about 30 seconds until fragrant—be careful not to burn it; it should smell warm and pungent.
Add the sliced carrots to the pot, stirring to coat with oil and aromatics, then cook for another 5 minutes until they start to soften and release a sweet scent.
Meanwhile, toast the cumin seeds in a small dry skillet over medium heat until fragrant, about 1 minute, then grind them using a mortar and pestle or spice grinder.
Pour in the vegetable stock and add the rinsed lentils, stirring to combine. Bring the mixture to a gentle boil, then lower the heat to a simmer.
Cover the pot partially and let everything simmer for 25-30 minutes, until the carrots are tender and the lentils have broken down, thickening the soup naturally.
Use an immersion blender directly in the pot to blend the soup until smooth and velvety, or carefully transfer to a blender in batches, blending until silky and smooth.
Season with salt, pepper, and a squeeze of lemon juice, stirring well to brighten the flavor.
Finish by drizzling with the remaining olive oil or adding a splash of coconut milk for extra richness, then serve hot in bowls garnished with herbs if desired.
