Heat olive oil in a soup pot. Add the vegetables, stir to coat with the oil, and let cook 5 minutes. Add ground cumin, let cook about another 5 minutes, until onion is softened.
Wash lentils, and add them to pot. Add broth, and bring to a boil. Lower the heat until the soup comes down to a simmer.
Let simmer 45 minutes to an hour.
Serve. Add about a teaspoon of wine vinegar, or to taste, to each bowl.
Notes
This is a simple, basic Foundation recipe for lentil soup. It is good as is - and it lends itself to variation.