Preheat oven to 450 F. In a small bowl stir together tapenade, fennel seeds, and zest. In a medium bowl blend flour, cayenne, butter, Fontina, and a pinch of salt until mixture resembles coarse meal. Add ice water and toss mixture until it just forms a stiff dough. On a lightly floured surface roll out dough into a 1/8-inch-thick rectangle and spread half of it with tapenade mixture. Fold remaining half over tapenade. Brush dough with egg and with a cookie cutter or sharp knife cut into squares. Bake crackers on a baking sheet in middle of the oven 8 minutes, or until golden, and transfer to a rack to cool . Serve crackers warm.