Sear the Beef: Heat olive oil in a large heavy-bottomed pot or Dutch oven over medium-high heat. Add the beef cubes in batches and sear until browned on all sides. Remove and set aside.
Sauté Aromatics: In the same pot, add chopped onion, carrots, and celery. Cook for 5–7 minutes until softened. Add garlic and cook for another minute until fragrant.
Add Seasonings: Stir in thyme, paprika, cumin, salt, and pepper. Mix well to coat the vegetables in spices.
Add Lentils and Broth: Add the rinsed lentils, seared beef, diced tomatoes, and beef broth. Stir everything together and add the bay leaves.
Simmer: Bring to a boil, then reduce heat to low. Cover partially and simmer for 1 to 1½ hours, stirring occasionally, until the beef and lentils are tender.
Finish and Serve: Discard bay leaves. Stir in fresh parsley and lemon juice. Adjust seasoning to taste.