We didn't have any chile peppers during the lockdown. (Well, I did for a brief moment...but I used them to make the
Mint Zhoug.) So I used red chili flakes, also known as crushed red pepper. I did add a few dabs of harissa to give the dish additional spice. You can certainly add a diced fresh chili or two to the onion and garlic mixture and skip the dried chili flakes.
Feel free to stir a generous handful of torn greens, such as kale or spinach, into the tomato sauce and let it wilt a minute, covered, before cooking the eggs. Cubes of feta can be added around the eggs while they are cooking, too.
Everyone likes their eggs cooked differently so rather than relying strictly on cooking times, keep an eye on them and the Shakshuka is ready when the eggs are cooked to your liking. Note they will appear less-cooked than they are, visually, but a slight nudge will let you know if they are cooked to your liking.