Preheat oven to 375 degrees F. Coat a large rimmed baking sheet with cooking spray.
Cut a small slice off the bottom of each squash half so it will sit nicely when stuffed. Brush the insides with 1 tablespoon oil and sprinkle with ¼ teaspoon salt. Place the squash cut-side down on the prepared pan. Bake until tender but still firm, 40 to 45 minutes.
Meanwhile, finely grind cinnamon stick, coriander and cumin seeds in a spice grinder or mortar and pestle. Tap the mixture into a small bowl and stir in paprika, smoked paprika, cayenne to taste, turmeric and the remaining ½ teaspoon salt.
Heat the remaining 2 tablespoons oil in a large pot over medium-high heat. Add onion and garlic and cook, stirring often, until starting to brown, 3 to 5 minutes.
Stir the spice blend into the onion and add cubed squash; cook, stirring, for 30 seconds. Add chickpeas, tomatoes and their juice and water. Bring to a boil. Reduce heat to maintain a gentle simmer, cover and cook, stirring occasionally, until the squash is tender but still firm, about 10 minutes. Stir in cilantro.
Fill each baked squash half with about 1 cup of the chickpea stew.
