Red Lentil Soup with Saffron

Name: Red Lentil Soup with Saffron
Ingredients: 3 tablespoons extra-virgin olive oil; 2 medium carrots, finely diced; 2 stalks celery, finely diced; 1 large onion, finely diced; 3 cloves garlic, minced; 1 tablespoon tomato paste; ½ teaspoon ground cumin; ¼ teaspoon crushed saffron threads; ¼ teaspoon ground turmeric; 4 cups low-sodium no-chicken or chicken broth; 1 ½ cups water, plus more as needed; 1 pound red lentils (2 cups), picked over and rinsed; 5 ounces spinach, coarsely chopped; 1 teaspoon kosher salt; 1 teaspoon ground pepper; Plain yogurt & chopped fresh mint for garnish