Heat a chargrill pan over medium high heat. Spray capsicum and zucchini with oil and chargrill for 2–3 minutes each side or until charred. Cool capsicum, remove skin and slice.
Layer capsicum, zucchini, tomato, cheese and ham on 2 slices of bread. Drizzle with sauce. Top with remaining bread. Spread with a little butter.
Reheat pan over medium heat. Add sandwiches, buttered-side down, to pan. Cook for 4–5 mins or until golden. Spread top of bread with remaining butter. Turn sandwich over, press down firmly and cook for a further 4–5 mins or until golden and cheese has melted.