Everything Spice Dough:
Place the work bowl of the food processor on the scale, set the scale to zero, and weigh the flour into the bowl. Weigh in the butter and add the spice mix and salt. Move the bowl to the food processor base, insert the metal blade, cover, and use the Pulse function to cut the flour and butter into flour-covered pea-sized pieces, about 15 quick pulses. Add the ice water all at once and process until the dough almost comes together in a ball. All the flour will be dampened and the dough will clump.
Spend time on this next step because the more compact and precise the dough, the easier it is to roll to the correct size and thickness. Form an X with two long pieces of overlapping plastic wrap and lightly flour the surface. Dump the dough onto the center of the plastic wrap, scraping the processor bowl clean. Wrap the sloppy gathering of dough in plastic and, at the same time, use a bench scraper (not your warm hands that might melt the butter clumps) to form the dough into a 4-inch disk or a 3½- by 3½-inch block. Once wrapped, use a rolling pin to gently press across the surface of the dough, then flip it over and do the same on the other side. Now let it rest: Refrigerate the dough for at least 4 hours or preferably overnight. Alternatively, slip the plastic-wrapped dough block into a ziptop bag and freeze it for up to 3 months. Defrost gently, overnight in the refrigerator.
Everything Spice Mix:
In a small jar, mix the poppy seeds, sesame seeds, onion, garlic, and salt. Cover and store in the refrigerator.
Lox and Schmear Tart:
Line a baking sheet with parchment. Lightly dust the counter with flour and roll the dough to a 12-inch round. With a paring knife or pizza wheel, trim to a 10-inch round. Lift the dough using a bench scraper or offset spatula and briskly transfer to the baking sheet; roll it over the pin or fold it gently, do what’s needed—be brave and adjust the shape as needed after moving.
Cut out a round in the center of the dough about 3 inches in diameter, using a glass or a cookie cutter, so the tart shell looks like an oversized bagel. With a small round cutter (I used the large end of a pastry tip), cut out small rounds from the dough trimmings and the center cutout, then make tiny holes in the centers (with the small end of the pastry tip or a bamboo skewer) to make small bagel shapes.
Pierce the dough all over with a fork or a docking tool. Brush the edge of the bagel circle with egg wash and place the tiny bagels atop the edge, decoratively. Brush the edges with egg wash. Chill the dough for 20 to 30 minutes.
Place a Baking Steel, baking stone, or inverted baking sheet on the center rack and heat the oven to 400°F.
Cut a piece of foil or parchment paper slightly larger than the size of the dough and spray one side with cooking spray. Lay it on top of the unbaked crust with the sprayed side facing down. Make sure there is enough paper overhanging the edges of the dough for easy lifting later. Fill generously with pie weights, uncooked beans, raw rice, pennies, or granulated sugar, keeping the decorated edges free of the weights.
Bake with the weights for 20 minutes, until golden brown and crisp on the edges.
Carefully remove the paper holding the weights and pop the pastry back in the oven to dry out the pie crust, about 10 more minutes.
Cool the crust in the pan on the rack. It may be baked a few hours, or even a day, in advance and kept covered on the counter, awaiting filling. Do not refrigerate.
Combine the onion and water in a small bowl and let soak for at least 5 minutes. This will remove any sharpness. In a medium bowl, use a sturdy spoon to beat the cream cheese until lightened, then add the scallions, chives, parsley, lemon juice, and salt and mix well.
To assemble the tart, drain the water from the onions and dry them well on a paper towel. Spread the cream cheese mixture across the tart shell with an offset spatula. Decoratively place the thin slices of tomato all around and mound the slivered salmon over the tomato. Top with the red onion and capers, garnish with chives, and serve with lemon wedges.
Excerpted from When Pies Fly: Handmade Pastries from Strudels to Stromboli, Empanadas to Knishes to Knishes by Cathy Barrow (copyright © 2019 by Cathy Barrow). Reprinted with permission from Grand Central Publishing. All rights reserved.