Heat the oil in a medium cast iron skillet over medium heat. Add the onion and cook until softened and slightly browned. Add in the zucchini and bell pepper and stir until they develop a bit of colour. Then add in the garlic and saute for an extra 30 seconds until fragrant.
Add in the tomato sauce, spinach, cumin, paprika and cayenne and stir until combined. Season with a pinch each of salt and pepper then create 4 wells in the mixture.
Crack the eggs into the wells and transfer the pan to the oven. Bake for 5-7 minutes or until the egg whites are cooked through but the yolks remain slightly runny.
Garnish with feta cheese and za'atar and serve with crusty bread.