Start by rinsing and draining the red lentils.
Heat the olive oil in a large pot over medium-high heat, and sauté the onions and garlic for about two to three minutes, until the onions are translucent.
Add the chopped carrots, and continue to sauté for another five minutes, until they start to soften.
Add the tomato paste, and all other spices and stir to combine until aromatic.
Then, add the rinsed and drained red lentils to the pot, and stir to combine with the other ingredients.
Add six cups of water or broth to the pot, and bring the mixture to a boil.
Reduce the heat to medium-low, cover the pot, and simmer for about 45 minutes, or until the lentils and vegetables are fully cooked and tender.
Optional - Using an immersion blender or a regular blender, puree the soup until it is smooth and creamy.
Season the soup more if necessary, add the lemon juice and give it a final stir.
Serve the soup hot, with more fresh lemon juice and some chopped parsley.