Heat the olive oil in a large skillet over medium heat. Add the diced onion and cook, stirring, until softened, about 5 minutes.
Add the bell pepper and minced garlic. Cook until the pepper begins to soften and the garlic is fragrant, 3–4 minutes.
Stir in the diced tomatoes, cumin, paprika, chili powder, and (if using) red pepper flakes. Season with salt and black pepper.
Bring to a simmer and cook uncovered until the sauce thickens slightly, about 10 minutes. If the sauce gets too thick, add a splash of water.
Use the back of a spoon to make 6 small wells in the sauce. Crack one egg into each well, keeping yolks intact.
Cover the skillet with a lid (or a large plate) and cook until the egg whites are set but yolks are still soft, 5–7 minutes. Cook longer for firmer yolks.
Remove from heat. Sprinkle with feta (if using) and fresh herbs. Serve straight from the pan with pita or crusty bread for scooping.