Heat a large heavy-bottomed pan over medium heat, then add a tablespoon of olive oil. Once shimmering, add diced onions and minced garlic, cooking until fragrant and golden—about 8 minutes, stirring often.
Sprinkle in the ground cumin, coriander, and cinnamon, then toast the spices for 1-2 minutes until they release their warm, smoky aroma. Stir constantly to prevent burning.
Add the chopped carrots and zucchini chunks to the pan, stirring to coat with the spices. Cook for about 5 minutes until the vegetables start to soften and catch a little color.
Pour in the canned crushed tomatoes and vegetable broth, stirring well to combine everything. Bring the mixture to a gentle simmer, then cover the pan and reduce the heat to low.
Stir in the drained chickpeas, then let everything simmer gently uncovered for about 20–25 minutes. During this time, the sauce will thicken and deepen in flavor, and the vegetables will become tender.
Uncover and stir in salt, pepper, and a squeeze of fresh lemon juice. Taste and adjust the seasoning as needed to balance the spices and brightness.
Turn off the heat and let the stew rest for 5 minutes, uncovered, to allow flavors to meld. Garnish with chopped fresh cilantro or parsley before serving.
Serve hot, spooned over rice, couscous, or with crusty bread, and enjoy the cozy, fragrant flavors of this comforting tagine.