In a heatproof bowl pour enough boiling water over tomatoes to cover and let stand for 15 minutes, or until soft. Drain tomatoes and pat dry.

Transfer pesto to a bowl, stir in olives and sun dried tomatoes.

Cut loaf diagonally into 4 pieces and halve each piece horizontally. Spread pesto on cut sides of bread and make 4 sandwiches with chicken, tomatoes, cheese, and onions.