This comes from Melissa Clark in NYTimes Cooking and makes a great meal on its own with some crusty bread or as a refreshing starter. Its bright, flavorful and can have a bite to it if you dial up the chili powder.
In a large pot of Dutch oven heat 3 Tbsp olive oil over medium/high heat. Stir in the chopped onion and garlic until fragrant and just beginning to soften – 3-4 mins. Add the tomato paste, ground cumin, chili powder and good grinding of salt and pepper. Stir well to combine and cook over medium heat until darkening – about 2 mins.
Add in the stock, water, lentils and carrot and stir well to combine. Bring the heat up to high and get the liquid to boil. Reduce heat to create a gentle simmer and place the lid partially over the pot. Let it simmer like this until the lentils and carrot has softened – about 30 mins.
Remove from heat and use an hand immersion blender to puree some of the soup, but not so much that it is all smooth – leave it a bit chunky. Stir in the lemon juice and let it stand, covered, for a bit (20-30 mins) to solidify all of the flavors.
Serve with crust bread and further dusting of chili powder if you want t bit of kick.