|(Food Styling/Sheryl Julian &Amp; Jill Gibson; Aram Boghosian for The Boston Globe)|
Make this in a glass pie pan or a French tart pan with a removable base. In either case, press the dough into the pan with your hands.
|1 1/4||cups flour|
|1/2||cup (1 stick) cold butter, cut up|
|4||tablespoons ice water|
|Extra flour (for sprinkling)|
1. In a food processor, combine the flour, salt, and butter. Pulse until dough is reduced to small pieces of butter.
2. Add the water and pulse again until the dough forms large clumps; do not let it come together to form a ball.
3. Turn the clumps out onto a lightly floured counter. Shape the mixture into a disk, flatten it with your hand to a 6-inch round. Wrap in foil and refrigerate for 20 minutes.
|1 1/3||cups half-and-half|
|2||tablespoons Dijon mustard|
|Salt and pepper, to taste|
|2||cups cooked onions|
|2||ounces Gruyere cheese, shredded (about 2/3 cup)|
1. Set the oven at 350 degrees. Have on hand a 9-inch glass pie pan. Remove the pastry from the refrigerator, unwrap it, and let it sit out for 5 minutes.
2. In a large bowl, whisk together eggs, half-and-half, mustard, salt, and pepper.
3. Set the dough in the center of the pie pan. Using your hand, push the dough toward the edges of the pan until it covers the pan evenly. Form a thicker rim at the top of the pie pan, tucking the dough under at the top to make a neat edge.
4. Spread the onions in the dough. Pour in the egg mixture and smooth the top. Sprinkle with cheese.
5. Bake the tart for 45 minutes, or until the eggs are set and the pastry is golden brown. Cool slightly before slicing. Serve warm or at room temperature.