Curried Red Lentil Soup

This is a really simple and cheap soup to make. It's based on a McDougall recipe which I have modified slightly.

2 cups chopped onion
2 cloves garlic, minced
7 1/2 cups water
1 tsp turmeric
3/4 tsp ground cumin
1/2 tsp ground ginger
1/4 tsp freshly ground black pepper
1/8 tsp cayenne
1 1/2 cups red lentils
2 medium potatoes, finely diced
1 carrot, finely diced
1 tsp red wine vinegar
2 Tbsp chopped fresh parsley or cilantro

Saute the onion and garlic in 1/2 cup of the water in a large pot until the onion is soft, about 5 minutes. Add the seasonings and cook for 1 minute. Add the lentils, potatoes and carrots and the remaining water. Bring to a boil, reduce heat and simmer for an hour. Stir in the vinegar and garnish with parsley or cilantro before serving.