Onion Jam and Goat Cheese Rugelach

Beat butter, cream cheese, and salt with a stand mixer fitted with the paddle attachment on medium speed until fluffy and creamy, about 2 minutes. With mixer running on low speed, gradually add flour, beating until soft, large clumps form, about 1 minute, stopping to scrape sides as needed. Turn dough out onto a clean work surface. Knead until dough just comes together. Divide dough in half; pat each half into a 5-inch disk. Wrap each disk in plastic wrap; refrigerate at least 2 hours or up to 2 days.

Heat oil in a large Dutch oven or a large, wide saucepan over medium. Add onions and salt; stir to coat onions in oil. Cover and cook, stirring occasionally, until onions soften and start to brown, 10 to 12 minutes. Stir in wine, sugar, vinegar, sumac, coriander, and pepper. Let mixture come to a boil. Reduce heat to low; simmer, partially covered, stirring occasionally and spreading onions in an even layer, until onions are sitting in a small pool of liquid, about 30 minutes. Uncover and cook, stirring occasionally, until onions are dry and just starting to stick to bottom of Dutch oven, 25 to 30 minutes. Spread cooked onions in an even layer on a large plate; let cool 30 minutes.

Remove 1 dough disk from refrigerator, and unwrap. Roll out dough on a lightly floured surface to about a 12-inch circle (about 1/8 inch thick). Trim off and discard any ragged edges. Using a small offset spatula, spread half of onion mixture (about 3/4 cup) evenly over dough. Sprinkle evenly with 1/2 cup goat cheese. Using a pizza cutter or sharp chef’s knife, cut circle evenly into quarters. Cut each quarter into 4 wedges to yield 16 long, thin wedges. Roll up each wedge starting at the wide end. Arrange rolled rugelach 2 inches apart with pointed ends facing down on 2 rimmed baking sheets lined with parchment paper. Chill 30 minutes.

Preheat oven to 350°F. Brush tops of rugelach with some of the beaten egg. Bake in preheated oven until golden brown and tops are crisp, 30 to 35 minutes, rotating pans from front to back halfway through bake time. Immediately transfer rugelach to wire racks; let cool about 15 minutes. Repeat steps 3 and 4 with remaining dough, filling, goat cheese, and beaten egg.