Heat the large heavy-bottomed pot over medium heat and add the olive oil, shimmering as it warms.
Add the diced onion to the pot and sauté, stirring often, until translucent and fragrant—about 5 minutes—until it starts to turn golden around the edges.
Stir in the minced garlic and cook for 30 seconds, just until it becomes fragrant and slightly soft, taking care not to burn it.
Add the sliced carrots and cook for another 5 minutes, stirring occasionally, until they begin to soften and release a sweet aroma.
Sprinkle in the cumin and smoked paprika, then toast the spices in the oil for about a minute, stirring constantly to deepen their aroma and flavor.
Pour in the vegetable stock and bring the mixture to a gentle simmer. Add the rinsed lentils, stirring to combine.
Lower the heat and let the soup simmer uncovered for 20-25 minutes, stirring occasionally, until the carrots are tender and the lentils have started to break down.
Check the tenderness of the carrots and lentils; they should be soft but still hold some shape. Taste and season with salt and pepper as needed.
Use an immersion blender to blend the soup directly in the pot, pulsing for about 30 seconds until it’s velvety with some texture left for interest.
Adjust the seasoning again, adding a squeeze of lemon juice if desired to brighten the flavors.
Finish the soup with a drizzle of good olive oil, stirring gently to incorporate, and serve hot, garnished with fresh herbs if you like.
