Put the glass tray on the wire shelf, place a baking sheet on the glass tray, and spread the pastry sheet on top.
Using a knife, lightly score a line around the pastry sheet, 1 cm from the edge. (Note: Do not cut all the way through.) Inside the scored line, prick all over with a fork."
Spread the Dijon mustard over the pastry, inside the scored line.
Arrange the tomato slices on top of the mustard. Sprinkle the salt and pepper over the tomato slices. Drizzle olive oil over the whole tart.
Slot the shelf into the middle shelf position, and cook on Combi 5 for 15 minutes.