Heat the olive oil in a large pot over medium heat. Add the diced onion and cook for 5 minutes until softened. Stir in the minced garlic and cook for 1 minute more.
Add the cumin, coriander, cinnamon, turmeric, and cayenne pepper. Stir for 30 seconds until the spices smell fragrant. Add the cubed pumpkin and sliced parsnips. Cook for 3 minutes, stirring to coat the vegetables with spices.
Pour in the diced tomatoes and vegetable broth. Add the chickpeas, salt, and black pepper. Bring the mixture to a boil, then reduce the heat to low. Cover and simmer for 25 minutes until the pumpkin and parsnips are tender.
Remove the pot from the heat. Stir in the lemon juice. Ladle the stew into bowls and top each serving with chopped cilantro.