large cup red or yellow lentils (about 200 grams or 1 cup) • oil • medium potato, diced • small onion, finely chopped • garlic clove, minced • medium carrots, diced • large tomato, diced • salt • cumin • black pepper • warm water (about 1.4 liters) • Celery, parsley, or fresh cream (optional, for garnish) •