Lentil soup on a snowy winter day

1 tablespoon olive oil
2 cups chopped onion
1 teaspoon ground turmeric
1 teaspoon ground cumin
1 teaspoon chili powder
1 teaspoon ground red pepper
1/4 teaspoon salt
1/4 teaspoon black pepper
2 garlic cloves, minced
3 1/3 cups water
2 1/3 cups dried lentils
1/3 cup chopped fresh cilantro
3 (14 1/2-ounce) cans vegetable broth
1 (28-ounce) can diced tomatoes, undrained

Heat olive oil in a large Dutch oven over medium-high heat. Add the onion; sauté for 3 minutes or until tender. Add the turmeric and the next 6 ingredients (turmeric through garlic); sauté for 1 minute. Add water and next 4 ingredients (water through diced tomatoes); bring to a boil. Reduce heat; simmer 1 hour.
Reserve 2 cups lentil mixture. Place half of remaining mixture in blender; process until smooth. Pour pureed soup into a large bowl. Repeat procedure with other half of remaining mixture. Stir in reserved 2 cups lentil mixture.