Preheat oven to 350°F (180°C). Line a 13 x 9-inch baking dish with parchment paper, letting excess extend over sides of pan.: As the oven warms, you will notice a gentle heat that readies the air for even baking; this steady temperature ensures the crust browns uniformly while the filling sets properly. Lining the pan with parchment makes lifting the bar slab simple after chilling, and the overhanging edges act like handles so you do not disturb the bars when removing them. A common error is to skip the parchment, which can make removal messy or cause the bars to stick; always allow the paper to overlap the sides so you can lift the tray cleanly. If your oven runs hot, place a tray on the middle rack and monitor the first batch so the edges do not darken too quickly.
For crust: In the bowl of a stand mixer fitted with the paddle attachment, whisk together flour, sugar, salt, and baking powder by hand. Add cold butter, and beat at medium speed until crumbly. Add egg, beating until combined and dough sticks together when pressed. Reserve 1 cup (130 grams) mixture in a small bowl; press remaining mixture into bottom of prepared pan.: You will feel and hear the dry ingredients turning into coarse crumbs as cold cubes of butter work through the flour, releasing tiny pockets of fat that bake into tender flakes. The mixture should look like coarse sand with pea to marble sized bits of butter . Adding the egg brings moisture and cohesion; the dough should hold when you press a handful. Reserving a cup of the crumb mixture creates a streusel like topping that will bake crisp. Avoid overmixing which warms the butter and yields a less flaky crust. If the dough feels greasy, chill it for a few minutes before pressing into the pan to prevent shrinking during baking.
Bake for 18 minutes. Leave oven on.: As the crust bakes, it will emit a faint, toasty aroma and begin to firm so it can support the filling. You should notice the edges becoming lightly golden while the center remains paler, indicating it is set but not overbaked. This partial bake stabilizes the base to prevent a soggy bottom once the filling is added. A common mistake at this stage is baking until the crust is fully brown, which can cause it to become overly crisp when baked again with the filling. Keep a watch for visual cues rather than relying only on the clock.
For filling: In a large heavy-bottomed saucepan, bring 3 cups (312 grams) cranberries, sugar, applesauce, orange zest, and salt to a boil over medium-high heat, stirring frequently until sugar dissolves. Reduce heat, and simmer, stirring occasionally, until cranberries begin to burst and mixture has thickened slightly, about 10 minutes.: The mixture will begin vocalizing its arrival with lively bubbling and a sweet citrus steam; the sugar should melt and coat the berries, and you will see glossy syrup form. Stirring helps prevent hot spots and ensures the orange zest oils disperse, contributing aromatic notes. If the mixture scorches on the bottom, the flavor will turn bitter, so keep the heat moderate and scrape the pan as needed. Using a heavy bottomed pot prevents burning and encourages even simmering.
In a small bowl, whisk together cornstarch and 1 1/2 tablespoons (22.5 grams) water until smooth; stir into cranberry mixture. Cook until thickened, about 2 minutes. Remove from heat; stir in remaining 2 cups (208 grams) cranberries. Spread mixture in an even layer onto prepared crust. Sprinkle reserved 1 cup flour mixture and pecans onto cranberry mixture.: Here you will notice the cranberries transform from firm spheres to softened jewels that pop under the spoon, releasing bright, tangy juices. The sound shifts to a gentler bubbling and the texture becomes more cohesive. This step concentrates flavors and helps the filling approach that jamlike body, which allows it to set when cooled. Avoid boiling too vigorously which can break down the fruit too quickly and make the texture mealy. Stir occasionally to gauge progress and scrape the sides to incorporate any sticking bits.
Bake until crust is golden brown and filling is bubbly, 30 to 45 minutes. Let cool completely in pan on a wire rack. Refrigerate until firm, about 1 hour, or freeze for 15 minutes.: The cornstarch slurry will suddenly thicken the filling, giving it a glossy, cohesive sheen that signals readiness; this happens quickly, so you will see the bubbling slow and the liquid transform into a more syrupy body. Stirring it in ensures there are no lumps, and after two minutes the mixture should cling to a spoon. Folding in the reserved whole cranberries at the end preserves freshness and contrast with softer cooked berries. Spread the filling evenly across the parbaked crust so each bar bakes uniformly. Scatter the reserved crumb mixture and pecans on top to create a crunchy, golden finish; a common error is piling too much topping in one spot which can lead to uneven baking, so distribute it evenly.
Using excess parchment as handles, remove from pan, and cut into bars. Store in an airtight container for up to 4 days.: During this bake the top will crisp, the pecans will toast, and the filling will bubble around the edges, indicating it has thickened and set. You will notice a rich aroma of caramelized sugar and toasted nuts. Cooling completely is essential so the internal structure firms and slices cleanly; rushing this leads to gooey bars that fall apart. Chilling in the refrigerator helps the bars slice into neat squares, and a brief stint in the freezer speeds the process if you are short on time. Avoid cutting while warm, which causes messy, dragging slices.
Using excess parchment as handles remove from pan and cut into bars Store in an airtight container for up to 4 days: Lifting the slab by the parchment makes transfer effortless, and when you slice, use a sharp knife wiped between cuts for clean edges. The bars should have a set filling with glossy pockets of cranberry and a golden, crumbly top with toasted pecans . Store in a sealed container to maintain texture; refrigeration keeps them firm for several days. A common pitfall is leaving them uncovered which causes the crust to soften and lose its crispness.