Add the onion, garlic, sweet potatoes, carrots, chickpeas, diced tomatoes, and vegetable broth to the slow cooker.
Stir in the cumin, cinnamon, ginger, smoked paprika, salt, and black pepper until evenly combined.
Cover and cook on low for 6 to 8 hours, until the sweet potatoes are soft.
Stir in the spinach and let it cook for 5 more minutes until wilted.
Ladle into bowls and top with cilantro and a squeeze of lemon.