1 teaspoon olive oil
1 1/2 cups chopped red onion
salt and pepper to taste
1 (28 ounce) can diced tomatoes
1 1/2 cups frozen chopped spinach
2 cups dry red lentils
2 cups water
2 teaspoons dried basil
1 1/2 teaspoons ground cardamom
1 teaspoon ground cumin
1/2 teaspoon ground cayenne pepper
1/2 teaspoon curry powder
Heat the oil in a large pot over medium heat, and cook the onion until golden brown. Season with salt and pepper. Mix in tomatoes, spinach, and lentils, and pour in water. Season with basil, cardamom, cumin, cayenne pepper, and curry powder. Bring to a boil, reduce heat to low, and simmer 25 minutes, stirring occasionally, until lentils are tender.
Transfer the soup to a blender (or use a hand held blender), and blend until smooth before serving.