Zwiebelmarkt means “onion market” referring to the onion festival held every fall in the medieval Swiss city of Bern. The festival is a cherished tradition dating back to 1403 when a raging fire nearly demolished Bern, leaving the city economically hard-pressed. Generous farmers from a nearby town brought relief to the citizens of Bern in the form of onions which grew abundant in their fields. At the festival, onion tarts such as this one are sold as warm wedges on crisp sheets of parchment paper.
SWISS ONION TART
2 cups plus 3 Tablespoons all-purpose flour
1 teaspoon salt, divided
10 Tablespoons lightly salted butter (cold)
4 to 6 Tablespoons ice water
1/4 pound sliced bacon, diced
8 cups thinly sliced yellow onions (about 2 pounds)
1 teaspoon sugar
1 cup heavy cream
1 cup whole milk
1/2 teaspoon caraway seeds
1/4 teaspoon freshly ground white pepper
1. Mix 2 cups flour and 1/4 teaspoon of the salt in a medium bowl. Cut in the butter until mixture resembles coarse crumbs. Gradually stir in water with a fork until mixture cleans sides of bowl. Gather into a ball; knead 3 or 4 times on lightly floured surface. Refrigerate, wrapped in plastic wrap, for 30 minutes.
2. Heat oven to 400 degrees. Roll pastry 1/8-inch thick on lightly floured surface. Fold into quarters; ease and unfold into 10-by-1-inch tart pan. Trim pastry flush with edge. Pierce bottom in several places with fork. Refrigerate 15 minutes. Line pastry with aluminum foil; fill with dried beans or rice and place on a baking sheet. Bake until pastry is set, about 12 minutes. Remove foil and beans. Bake until pastry is cooked through and golden, 10-12 minutes. Cool on wire rack.
3. Reduce oven temperature to 350 degrees. Heat bacon in large skillet over medium heat until it begins to render some fat. Stir in onions and sugar. Cook over medium-high heat, stirring occasionally, until onions are soft and golden, about 15 minutes. Stir in the remaining 3 Tablespoons flour. Cool mixture to room temperature.
4. Whisk eggs lightly in large bowl; stir in cream and milk. Stir in onion mixture, remaining 3/4 teaspoon salt, caraway seeds, and white pepper. Carefully pour mixture into pastry shell. Bake on baking sheet for 25 minutes. Increase oven temperature to 400 degrees, and continue baking until custard is set and the top is light brown, about 5 to 10 minutes. Cool on wire rack for 10-15 minutes, then serve warm. Makes 8-10 servings.