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1
Preheat the oven to 425 degrees.
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2
Put the flour, baking powder, and a pinch of salt in the bowl of a food processor fitted with a steel blade.
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3
Add the butter, and pulse in short spurts until crumbly.
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4
Drizzle in 1/3 cup ice water, and continue to pulse until the dough comes together into a ball.
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5
Wrap the dough in plastic wrap, and refrigerate for at least 30 minutes.
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6
Cut the tomatoes into 1/8-inch-thick rounds.
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7
Remove the seeds, then put the tomatoes in one layer on a large plate, and sprinkle with salt and freshly ground pepper to taste.
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8
Let sit for a few minutes.
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9
On a floured surface, roll out the dough to about 10 inches in diameter.
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10
Gently lay it in an ungreased 9-inch tart pan with a removable bottom, pressing the dough into the sides and trimming off any excess.
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11
Using a rubber spatula, spread the mustard over the bottom of the crust, and put the cheese on top.
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12
Drain and discard any liquid that has seeped out of the tomatoes, and then blot them dry with paper towels.
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13
Arrange the slices on top of the cheese, and scatter the olives over.
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14
Drizzle the olive oil over all, and sprinkle with the oregano, Parmesan cheese, and more freshly ground pepper to taste.
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15
Put the tart in the oven, and bake for about 30 minutes, or until the crust is golden.
