In stockpot over medium heat, cook paprika, cumin, cayenne pepper and cinnamon, stirring constantly, until aromatic, 20 to 30 seconds.
Increase heat to medium-high. Heat oil. Add onion, carrot, celery and garlic. Saute until onion is translucent, 3 to 5 minutes. Stir in tomato paste.
Add remaining ingredients except spinach and lemon juice. Bring to a boil. Reduce heat. Simmer until potato is tender, 10 to 15 minutes. Discard bay leaf.
Add spinach and lemon juice. Cook until heated through. Serve hot.