In a large pot, cook onion, celery, and carrots in olive oil until soft, for about 7 minutes. Add garlic, stir. Add tomato paste, stir.
Add lentils, garlic powder, broth, and 2 cups water. Bring to a boil, then reduce to a simmer. Cover the pot and cook until lentils are tender, about 35 minutes.
Add vinegar, 1 ¼ teaspoons salt, and ¼ teaspoon pepper, or more to taste. Serve with crackers or bread and butter.