In a small bowl, stir together the olives and lemon zest; set aside. In a blender, puree the tomatoes with their juice until smooth, about 30 seconds. Set aside. In a 12-inch skillet over medium, melt the butter. Add the onion and ½ teaspoon salt.

Cook, stirring, until softened, about 5 minutes. Stir in the garlic, cumin, coriander, cinnamon and pepper flakes, then cook until fragrant, about 30 seconds. Remove from the heat. Transfer ½ cup of the onion mixture to a large bowl and set aside.

Return the skillet to medium and add the broth and tomatoes. Bring to a simmer, scraping up any browned bits. Cover and cook until the flavors meld, about 15 minutes, stirring once about halfway through. Remove from the heat.

While the sauce simmers, stir the panko and ½ cup water into the reserved onion mixture. Let stand until the panko softens, about 5 minutes, then use your hands to mash to a smooth paste.

Add the beef, ½ cup of cilantro, and 1 teaspoon each salt and pepper. Mix thoroughly with your hands. Divide into 16 (2-tablespoon) portions, rolling them into smooth balls. Place on a plate, cover and refrigerate for 15 minutes.

Return the sauce to medium and bring to a simmer. Add the meatballs in a single layer, then spoon sauce over each. Cover, reduce to low and cook for 15 minutes. Flip each meatball, then continue to cook uncovered, stirring occasionally, until the sauce is slightly thickened and meatballs are cooked through, about 15 minutes.

Push the meatballs to the sides of the skillet. Taste and season the sauce with salt and pepper. Gently pour the eggs into the center, cover and cook over medium-low until the egg whites are barely set and yolks are still runny, 4 to 5 minutes. Off heat, sprinkle the olive mixture and remaining ½ cup cilantro over the tagine.