In a large 12'' skillet (make sure it has a tight-fitting lid), heat the olive oil over medium-high heat. Add the diced onion and red bell pepper, cooking until the onions are translucent and the peppers are soft.
Add the minced garlic and cook for 1 minute longer, making sure it doesn't burn.
Add the tomato paste, harissa paste (if using), and all of the spices, stirring for 1 minute to toast them and get a deeper flavor.
Carefully pour in the canned tomatoes, using a spoon or your hands to break them up into a sauce-like consistency.
Stir everything well, making sure that the spices are evenly distributed. Taste to check for seasoning and allow the sauce to come to a simmer.
Once bubbling, use a spoon to make wells into the sauce and crack an egg into each well. Cover the saucepan with the lid, adjust the heat to low, and allow the eggs to cook for around 7-8 minutes, until the whites are set. The yolks should be cooked just under your liking, as the residual heat will continue to cook the eggs as it sits.
Remove the pan from the heat and garnish with fresh parsley and crumbled feta. Serve the shakshuka warm with toasted bread and enjoy!
Notes
*You may need to adjust the amount of harissa you put into the sauce, as each brand varies in spiciness. If you don't have it, harissa paste can easily be substituted with tomato paste.