Line a baking sheet with parchment paper (or use parchment from pastry wrap). Unroll pastry (it should be a 10-inch square) and place on parchment paper. Use the tines of a fork to press a 1-inch (2.5 cm) border around edge of pastry. Prick pastry all over with a fork.
In a small bowl, whisk egg and water together; brush lightly over entire surface of pastry. Bake for 17 to 22 minutes or until pastry is golden brown all over top and bottom. While pastry is in the oven, slice tomatoes thinly. Once ready, transfer pastry to a rack to cool completely.
Once, cooled, spread cheese evenly over cooled pastry, leaving border open. Layer tomatoes over cheese. Drizzle with olive oil; sprinkle with salt and scatter basil over top. Season with fresh black pepper (if desired). Cut into 9 squares to serve.
PER SERVING: 542 calories, 18 g protein, 39 g fat (13 g saturated fat), 31 g carbs, 2 g fibre, 82 mg cholesterol, 331 mg sodium.