Wash the tomatoes, pat dry, slice into 1 cm thick rounds, and remove the seeds. Discard the first and last slices, lightly salt both sides of the remaining slices, and arrange on a large platter to draw out excess moisture.
Preheat the oven to thermostat 7½ (about 240°C). Roll out the dough to ½ cm thickness and line a 30 cm tart tin. Trim excess dough by rolling a pin over the edges, then crimp or flute the edges with your fingers, or fold and flute them before scoring lightly with a knife. Prick the base all over with a fork, avoiding the tin edges.
Cut the cheese into ½ cm thick strips.
Spread mustard evenly over the base, then layer with cheese slices. By now, the tomatoes will have released water—pat each slice dry with paper towels and arrange overlapping slightly on top of the cheese.
Scatter olives over the top, drizzle with olive oil, sprinkle with oregano, and bake for 30 minutes.
Remove from the oven, unmold onto a serving dish, and finish with freshly ground pepper. Serve hot or warm.
Source: C.I.D.I.L
