Heat a large soup pot or Dutch oven to medium-high heat. Add the onions, celery, and carrots. Cook for 3-4 minutes, stirring frequently, until the veggies start to soften. Add water, a tablespoon at a time, if they start to stick.
Add the garlic, cumin, smoked paprika, cinnamon, and salt. Mix to coat the vegetables.
Add the tomato paste, canned tomatoes, bay leaves, and fresh thyme. Mix well and simmer the tomatoes for about 5 minutes to start building the flavor.
Add the tomato paste, canned tomatoes, bay leaves, and fresh thyme. Mix well and simmer the tomatoes for about 5 minutes.
Add the lentils and 8 cups of vegetable broth. Bring the soup to a boil, then reduce it to a simmer, cover the pot, and cook for 45 - 60 minutes until the lentils are tender and the liquid has reduced. Check the soup periodically and add more broth depending on the consistency you want.
Serve the soup hot in bowls and garnish with lemon wedges, crush red chili flakes or chopped parsley if desired.