On a work surface, combine the frozen all-purpose flour, cake flour and 1/2 teaspoon salt. Add the cold butter and with a metal dough scraper, cut butter into 1/4 to 1/2-inch pieces. Add enough ice water just until the mixture almost holds together.

Turn out onto a lightly floured board and press together as best you can to form a rough rectangle shape. There will be large chunks of butter showing. Work quickly and do not knead. Roll out dough into a 1/2-inch thick rectangle. Fold the narrow ends towards the center to meet in the center. Fold in half again so that there are four layers. This is your first turn. Turn the dough a quarter of a turn. Roll again to form a 1/2-inch thick rectangle again. Repeat the folding process. This is your second turn. Repeat the rolling and turning one additional time. Fold the dough into thirds as you would a business letter, wrap the dough in plastic wrap and chill 45 minutes.

In the meantime, warm 2 tablespoons olive oil in a skillet over medium low heat. Add the onions and oregano and cook, stirring occasionally, until the onions are soft and golden, 40 to 50 minutes. Add the tomatoes and continue to cook until almost dry, 10 to 15 minutes. Season with salt and pepper and cool.

Preheat an oven to 400° F.

On a floured surface, roll the dough to a 13 by 9-inch rectangle, 1/4-inch thick. Crimp the edges. Place the dough on a baking sheet. Cover the dough to within 1/2-inch of the edge with the onion mixture. Sprinkle the cheese onto the top. Bake until the crust is a golden and crisp, 30 to 40 minutes. Drizzle with the remaining 2 tablespoons olive oil and serve immediately.

Makes 1 rectangular tart, 13" X 9-inches and serves 6