Heat olive oil in a 26 cm / 10-inch skillet over medium heat. Add the onion and cook for 4 to 5 minutes until soft and translucent.
Add garlic and red bell pepper. Cook 3 minutes until the pepper starts to soften.
Stir in cumin, smoked paprika and chili flakes. Cook 30 seconds until fragrant.
Pour in the crushed tomatoes, salt and black pepper. Simmer uncovered for 8 to 10 minutes, stirring occasionally, until the sauce thickens and coats the back of a spoon.
Stir in the spinach a handful at a time, letting each batch wilt before adding more, about 2 to 3 minutes total.
Taste the sauce and adjust salt. Use the back of a spoon to make 4 shallow wells in the sauce.
Crack one egg into each well. Cover the skillet and cook over medium-low heat for 5 to 7 minutes, until the whites are fully set and the yolks are still soft.
Remove from heat and scatter feta and parsley over the top.
Serve straight from the skillet with lemon wedges and warm bread.