How to Make It
Preheat oven to 325°F. Combine cranberries, sugar, lemon peel strip and lemon juice, a pinch of salt, and a pinch of pepper in a medium saucepan. Cook over medium-high, stirring and crushing cranberries with a wooden spoon, until cranberries have broken down and mixture has thickened, 10 to 14 minutes. Remove from heat, and stir in onion soup mix; let cool slightly, about 15 minutes.
Season brisket with remaining 2 tablespoons salt and remaining 1 teaspoon pepper. Layer 2 large sheets of heavy-duty aluminum foil in a large roasting pan, overlapping slightly to cover bottom of pan and letting foil extend 8 inches past both ends. Repeat with 2 additional sheets of foil placed crosswise (to form an “X”). Top with a sheet of parchment paper. Spread about a quarter of the cranberry sauce on center of parchment, and place brisket, fat side up, on top. Spread remaining cranberry sauce over top of brisket, top with another sheet of parchment, and wrap foil tightly around beef. Crimp to seal. Place roasting pan on a baking sheet, and braise brisket in preheated oven until fork-tender, 3 hours to 3 hours and 30 minutes. Uncover and let cool completely, about 1 hour and 30 minutes. Cover and refrigerate at least 8 hours or up to 2 days.
Preheat oven to 325°F. Uncover brisket, and discard any fat that has solidified on surface of brisket and pan drippings. Scrape off cranberry sauce, place in a bowl, and set aside. Transfer brisket to a carving board, and slice against the grain. Arrange brisket slices in an ovenproof serving dish, and spoon reserved cranberry sauce over top. Cover and bake in preheated oven until heated through, 45 minutes to 1 hour.