Puree the olives, oil, garlic, and zest in a food processor until smooth and spreadable. Blend in the mayonnaise. Toss the tuna, artichokes, lemon juice, and pepper in a medium bowl, keeping the tuna in small chunks.
Hollow out the bottom and top halves of the bread. Spread the olive puree over both cut sides of the bread. Spoon the tuna and artichoke mixture onto the bottom half of the bread. Sprinkle the tomatoes over. Cover with the bread top. Cut the sandwich crosswise into 6 pieces and serve.