Heat the olive oil in a large skillet or saucepan over medium heat.
Add the chopped onion and cook until softened and translucent, about 5 minutes.
Stir in the minced garlic and cook for another minute until fragrant.
Add the diced tomatoes and green bell pepper to the skillet. Cook, stirring occasionally, until the tomatoes break down and release their juices, about 10 minutes.
Stir in the ground cumin, ground coriander, paprika, black pepper, salt, and sugar (if using). Cook for another 2 minutes.
Pour in the water or vegetable broth. If using, add the cooked chickpeas or diced meat. Stir to combine.
Simmer the mixture over low heat for about 15-20 minutes, or until the sauce thickens and the flavors meld together.
Taste and adjust seasoning as needed.
Garnish with chopped fresh parsley before serving.
Enjoy your meal!