How to Make It
Hollow out the bread by removing most of the inside crumb. Reserve ½ cup of the crumb for the filling.
Place the olive oil, capers, parsley, garlic, anchovies, and ¼ teaspoon pepper in a food processor. Pulse until the garlic is finely chopped, 1 to 2 minutes. Transfer the mixture to a large bowl. Add the bell pepper, tomatoes, onion, olives, and the reserved bread filling. Toss to combine.
Layer half the mixture in the bottom half of the hollowed-out bread. Top with the hard-boiled eggs and the remaining mixture. Replace the top of the loaf. Wrap the filled loaf with plastic wrap. Weigh it down with a heavy object, such as a cast-iron skillet filled with cans. Place it in the refrigerator. Let sit at least 10 hours or overnight.
Before serving, cut the loaf into 6 wedges with a sharp bread knife.