My first attempt at an apple and onion tart yielded something that smelled delicious but looked like onion-spiked applesauce in a cookie crust—none too desirable!  The next time I thought ahead and decided to borrow elements from our favorite French tarts: the pissaladière, an anchovy and olive tart from the south of France that has a luscious base of caramelized onions and the classic tarte aux pommes with its beautiful decorative pattern of thinly sliced apples.  We then added cheese for a more nutty fall flavor and bit more ooze.  The resulting tart smells and tastes fantastic and looks the part.

Lydia took such gorgeous photos I had to share them all!

xoxosl

Apple and Onion Tart

Yield: Makes one 9-inch round tart (with a little dough left over) or one 1 9×13-inch rectangle tart,  one large crostata or 4 minis.

Note: dough must rest at least one hour and onion mixture needs to cool completely before assembling tart. Both can be done the day before.

1 Recipe pate brisée

2-1/2 cups all-purpose flour

1 teaspoon salt

1 teaspoon sugar

2 sticks unsalted butter, chilled and cut into small pieces

1/4 to 1/2 cup ice water

Tart ingredients

3-4 yellow onions, sliced into half moons

2 tablespoons unsalted butter

Kosher salt, to taste

3 tablespoons fresh thyme, roughly chopped, plus several whole sprigs for garnishing

3 teaspoons fresh rosemary, roughly chopped

1/4 pound gruyère cheese

3 red apples (Gala or other sweet and firm variety)

1/2 lemon

Egg Wash

1 egg yolk

1 tablespoon milk or cream

To make the tart crust:

In the bowl of a food processor, combine flour, salt, and sugar. Add butter, and process until the mixture resembles coarse meal, 8 to 10 seconds.

With machine running, add ice water in a slow, steady stream through feed tube. Pulse until dough holds together without being wet or sticky; be careful not to process more than 30 seconds. To test, squeeze a small amount together: If it is crumbly, add more ice water, 1 tablespoon at a time.

Alternatively, cut the cold butter into small cubes.  In a large bowl, combine the flour, salt and sugar.  Add the butter cubes and work to combine, using your thumb and forefinger to pinch the butter into the flour mixture.  Keep pinching until the mixture has a sand-like consistency.  Add a few splashes of the ice water and continue mixing with your hands until dough comes together in one ball, adding more water (up to the full half cup) bit by bit if necessary.

Divide dough into two equal balls. Flatten each ball into a disc and wrap in plastic. Transfer to the refrigerator and chill at least 1 hour. Dough may be stored, frozen, up to 1 month.

To make the tart:

Preheat oven to 400 degrees.

Peel and slice yellow onions into thin, half moon slices.

In a medium-sized skillet over medium-low heat, melt butter and add onions slices, tossing to cover with butter.  Cook, stirring occasionally until golden brown, about 10 minutes.  Sprinkle to taste with kosher salt. Add chopped herbs (reserving the sprigs of thyme to decorate the finished tart) and continue cooking until onions are a rich golden brown, about 10 minutes more.  Set aside to cool.

Please note that onions must be cooled before assembling tart.  They can be prepared the day before and kept covered in the refrigerator.

On a lightly floured surface, roll one dough ball to 1/8-inch thick.  Place in tart pan of your choice (you can use any shape tart pan), using the side of your hand to gently mold the dough against the scalloped tart pan edge.  Alternatively make one free-form crostata or cut the dough into 4 same-sized rounds to make mini-crostata.  Freeze the remaining dough ball for another time.

Using a sharp knife or cheese slicer, slice thin rectangular strips of the gruyere cheese.  You want enough to fill the whole tart.  Set aside.

Cut the apples in half and remove the core.  Cut thin slices, drizzling the exposed apple flesh with lemon juice to keep it from browning. Set apple slices aside.

Spoon the prepared onions into the tart shell, spreading them out to make an even layer.  Alternate apple and cheese slices on top of the onions in a desired pattern.  For example, if using a square or rectangular pan, build rows of apples and cheese.  If using a round tart pan, build circles from the outside in.  Crostata also look lovely if you build in a circular shape from the outside in.  If making crostata, leave a 2-inch border all the way around the pastry and simply fold the sides in and over the apple and cheese slices.

Fill in the empty space between rows with the reserved sprigs of fresh thyme.

In a small bowl, whisk together the egg yolk and milk or cream.  Using a pastry brush or your fingertips, brush the exposed dough with the egg wash.  This will help the crust brown beautifully.

Place in a hot 400 degree oven and bake until golden brown, rotating once halfway through cooking, about 1 hour.  If making crostatas, check oven regularly after the first half hour as the smaller tarts will brown faster and be ready anywhere between 40-55 minutes depending on the size.