Add the diced onion, sliced carrots, and minced garlic to the slow cooker.
Stir in the rinsed lentils, drained chickpeas, and diced tomatoes with their juices.
Sprinkle the cumin, coriander, cinnamon, turmeric, paprika, salt, and black pepper over the ingredients.
Pour the vegetable broth over everything and stir gently to combine.
Cover and cook on low for 7 to 8 hours or on high for 4 hours until the lentils are tender.
Stir in the lemon juice right before serving.
Ladle into bowls and top with chopped cilantro.