In a large pot or deep skillet, heat some oil over medium heat. Add the onion and sauté until translucent, about 5 minutes. Add the garlic and ginger and cook for another 1-2 minutes.
Stir in the tikka masala paste, turmeric, cumin, coriander, paprika, cinnamon, and salt. Cook for a minute to toast the spices.
Add the sweet potatoes and chickpeas to the pot, stirring to coat them in the spice mixture.
Pour in the diced tomatoes, vegetable broth, tomato paste, and coconut milk. Mix everything together well.
Bring the mixture to a boil, then reduce the heat and simmer for 20-25 minutes, or until the sweet potatoes are tender.
Taste and adjust the seasonings if needed.
Serve the tikka masala over cooked basmati rice, garnished with fresh cilantro.