Sauté the vegetables: In a large pot, heat the olive oil over medium heat. Add the chopped onion, garlic, carrots, and celery. Sauté for 5-7 minutes, or until the vegetables have softened and the onion is translucent.

1. Add the spices: Stir in the cumin, turmeric, smoked paprika (if using), salt, and pepper. Cook for 1-2 minutes to let the spices bloom and become fragrant.
2. Add the lentils, broth, and tomatoes: Add the lentils, vegetable broth, and diced tomatoes (with their juices) to the pot. Stir to combine, and bring the mixture to a boil. Once boiling, reduce the heat to low and cover the pot. Let it simmer for 25-30 minutes, or until the lentils are tender but still hold their shape.
3. Add the collard greens: Stir in the chopped collard greens and continue to simmer for another 5-10 minutes, until the greens are tender and the flavors have melded together.
4. Finish with lemon: Stir in the lemon juice and zest (if using), and taste the soup. Adjust the seasoning with more salt, pepper, or lemon juice if needed.
5. Serve: Ladle the soup into bowls and garnish with fresh parsley or cilantro if desired.
6. Enjoy your warm and comforting Lemony Lentil Soup with Collards!