Zwiebel Kuchen (onion Pie) Recipe

Preheat and prepare pan

Preheat oven to 400°F (200°C). Lightly grease a 10-inch (25 cm) tart pan or pie dish with a little butter and dust with flour or line with parchment.

Roll and fit pastry

On a lightly floured surface, roll the thawed puff pastry sheet to about a 12-inch (30 cm) circle to fit the pan with a slight overhang. Gently lift into the prepared pan, pressing into the edges and trimming excess so there is about 1/2 inch overhang. Fold the overhang under and crimp or press to form a neat rim. Prick the bottom lightly with a fork several times.

Chill the fitted crust in the refrigerator while you prepare the filling (10 minutes). Brush the rim lightly with melted butter.

Slice onions

Peel and halve the onions. Slice each half crosswise into thin slices (about 1/8 inch). You should have roughly 6 cups loosely packed.

Cook onions low and slow

Heat a large heavy skillet over medium heat. Add butter and olive oil. When butter foams, add the sliced onions, sprinkle with sugar and 1 teaspoon of the salt. Stir to coat. Reduce heat to medium-low and cook, stirring every few minutes, until the onions are soft and beginning to turn golden — about 25–30 minutes. If they begin to stick, add a splash of water.

Season

When onions are softened and lightly caramelized, stir in the remaining 1/2 teaspoon salt, 3/4 teaspoon black pepper and caraway seeds if using. Taste and adjust seasoning. Remove from heat and let cool for 10 minutes.

Prepare custard

In a medium bowl, beat the eggs. Add softened cream cheese and whisk until mostly smooth (a few small lumps are fine). Stir in sour cream, heavy cream and grated nutmeg until combined. Season lightly with additional black pepper. The mixture should be pourable but thick.

Assemble pie

Scatter about two-thirds of the cooked onions evenly over the chilled puff pastry base. Pour the egg and cream mixture over the onions, using a spatula to coax it into gaps. Top with the remaining onions, arranging them in an even layer. Gently press edges of the pastry rim to tidy the tart.

Bake

Place the tart on a baking sheet and bake in the preheated 400°F (200°C) oven for 25–30 minutes, until the pastry is puffed and golden and the custard is set (a slight jiggle in the center is okay). If the rim browns too quickly, tent loosely with foil.

Cool and garnish

Remove from oven and let cool for 10–15 minutes to set. Sprinkle with sliced fresh chives and a light grind of coarse sea salt and black pepper to taste. Slice and serve warm or at room temperature.