Prepare the Vegetables: Heat the olive oil over medium heat in a large pot. Add the chopped onions, garlic, celery, and carrots. Sauté until the onions become translucent and the vegetables start to soften; about 5 minutes.
Add the spice: Stir in the Moroccan spice blend and cook for another minute until fragrant.
Add the Beans and Tomatoes: Add the white beans, kidney beans, chickpeas, and canned tomatoes to the pot. Mix well to combine everything.
Simmer the Stew: Pour in the vegetable broth and add the chopped sweet potato. Bring the stew to a boil, then reduce the heat and simmer uncovered for about 20 minutes, or until the sweet potatoes are tender.
Season and Serve: Season the stew with salt and pepper to taste and a squeeze of lemon for brightness. Let it simmer for another 5 minutes.
Garnish and Serve: Remove from heat. Ladle the bean stew into bowls and garnish with fresh chopped cilantro. Serve hot.