Heat oil in a 12-inch skillet over medium heat. Sauté onion, red pepper, salt, and black pepper for 6-8 minutes until soft and translucent.
Lower the heat to medium-low, add garlic, paprika, cumin, and optional cayenne. Stir for 30 seconds.
Mix in tomatoes and harissa paste, then simmer for 15 minutes until the sauce thickens.
Stir in spinach and cook until wilted. Make 3-5 wells in the sauce with a spoon.
Crack eggs into the wells, cover, and cook for 5-8 minutes to your preferred yolk doneness.
Season with salt and pepper, then top with feta, parsley, avocado, and microgreens if desired. Serve with toasted bread.