Heat a deep, large skillet or sauté pan on medium. Slowly warm olive oil in the pan. Add chopped onion, sauté for a few minutes until the onion begins to soften. Add garlic and continue to sauté till mixture is fragrant.
Add the bell pepper, sauté for 5-7 minutes over medium until softened.
Add tomatoes, bell peppers and tomato paste to pan, stir till blended. Add spices and sugar, stir well, and allow mixture to simmer over medium heat for 5-7 minutes till it starts to reduce. At this point, you can taste the mixture and spice it according to your preferences. Add salt and pepper to taste, more sugar for a sweeter sauce, or more cayenne pepper for a spicier shakshuka (be careful with the cayenne... it is extremely spicy!).