Heat the olive oil in a large pot over medium heat. Add the onion, carrots, and celery with a pinch of salt. Cook, stirring occasionally, for about 8 minutes, until softened.

Add the garlic, cumin, and smoked paprika (if using). Cook, stirring constantly, for 1 minute until fragrant.

Stir in the lentils, vegetable broth, and bay leaf. Bring to a boil, then reduce heat to low, cover partially, and simmer for 25–30 minutes, until lentils are tender.

Remove from heat, discard the bay leaf, and stir in the lemon juice. Season with salt and pepper to taste.

Ladle into bowls, top with parsley, and serve hot.