Step 1

Combine the first six ingredients in a large pot and simmer for 10 minutes. Add half a can of beans, salt and cumin, and cook for 5 more minutes. Puree soup slightly in a blender {I used my Blendtec}, then return to pot. Add the rest of the beans.

Step 2

In a small mixing bowl, combine the cornstarch with 1 1/2 tablespoons of water. Add the lemon and the cornstarch mixture to the soup, and cook until thickened.