Place onion, capsicums and garlic in prepared pan. Season with freshly ground pepper, and sprinkle a little olive oil over them. Roast in preheated oven for about 10 minutes.
When the vegetables are tender, remove from oven. Spread tomatoes evenly over the vegetables, and sprinkle with feta cheese.
Place pastry over vegetables.
Bake for 20 minutes or until pastry is golden brown. Remove from oven, place a tray over the dish, and then flip it upside down so that you have a puff pastry base with the vegetables on top. Serve immediately while the puff pastry is still crisp.
You can cut it into smaller squares and serve as hors d'ouevres.