Heat olive oil in a large pot over medium-high heat. Add the ground beef and brown it, about 5–6 minutes. Season with salt and pepper, then remove and set aside.
In the same pot, sauté the onion, carrots, and celery for about 4–5 minutes until softened. Add the garlic and cook for another minute.
Stir in the tomato paste, cumin, smoked paprika, and thyme, coating the vegetables well.
Add the browned beef back to the pot, followed by the lentils, diced tomatoes, and beef broth.
Bring everything to a boil, then reduce heat to low and simmer uncovered for 35–40 minutes, until the lentils are soft and the beef is cooked through.
Taste and adjust seasoning. Ladle into bowls and top with fresh parsley.