In a large pot, heat the olive oil over medium heat. Add the diced onion, carrots, and celery. Sauté the mixture for about 5-7 minutes, stirring occasionally, until the vegetables are softened and the onion is translucent.
Add the minced garlic and diced red bell pepper to the pot, along with the ground cumin, smoked paprika, ground coriander, and cayenne pepper (if desired). Cook for an additional 2-3 minutes, stirring frequently, until the spices become fragrant and the bell pepper begins to soften.
Incorporate the rinsed lentils, diced tomatoes (with their juice), and vegetable broth into the pot. Stir all ingredients until well combined, then increase the heat and bring the mixture to a rapid boil.
Once boiling, reduce the heat to low and allow the soup to simmer uncovered for approximately 25-30 minutes, or until the lentils are tender. Stir the soup occasionally, and feel free to add more water or broth as needed if the soup thickens too much.
After the lentils have softened, season the soup generously with salt and freshly ground black pepper to taste. For a creamier consistency, consider using an immersion blender to purée a portion of the soup. Blend until your desired texture is achieved.
Serve the soup hot, garnished with a sprinkle of freshly chopped parsley. Pair with lemon wedges on the side for an added touch of brightness—squeezing the lemon juice over the soup just before eating enhances the flavors wonderfully.
Notes
Serve in rustic bowls with a drizzle of olive oil and warm crusty bread for dipping.