Heat a Dutch oven or soup pot (with cover) over medium to medium-high heat. Once hot, add olive oil and leek leaves. Saute leek leaves until bright green, fragrant, and soft.
Add ground turkey and cook, breaking into crumbles, until almost completely browned. Once the turkey is almost cooked, stir in the tomato paste and cook about 1 minute more.
Add the broth, sweet potatoes, chopped tomatoes, taco seasoning, and ground cinnamon to the turkey mixture and stir to mix. Adjust heat to high, and bring soup to a boil. Cover, reduce heat to medium-low, and simmer for 12-15 minutes or until sweet potatoes are tender.
Stir in drained and rinsed lentils and continue cooking until soup is heated throughout. Season with salt and pepper.
Serve warm with optional garnishes.
