Slow Cooked Mediterranean Lentil Soup

Ingredients

• 1 cup green lentils, rinsed
• 1/2 cup red onion, chopped small
• 5 cups vegetable broth
• 1/2 cup celery, chopped small
• 1/2 cup carrot, peeled and chopped small
• 1 small sweet potato, peeled and chopped small
• 3 cloves garlic, minced
• 1/2 teaspoon ground cumin
• 1 teaspoon lemon zest
• 2 teaspoons lemon juice
• 2 tablespoons dried oregano
• 2 tablespoons tomato paste
• 3 cups fresh baby spinach