Arrange your oven rack to the lower third of the oven. Preheat the oven to 350 degrees F. Spray two 5 x 8-inch loaf pans with nonstick spray.: You will notice a warm, steady hum as the oven comes up to temperature, and setting the rack low encourages even browning on the top while fully baking the center. This position helps the loaves rise uniformly without the crust overbrowning too quickly. A common pitfall is not preheating long enough, which can lead to uneven rise, so wait until the oven reaches 350 degrees F and the temperature holds for a few minutes before putting the pans in.
In a medium bowl, toss the pears with the white and brown sugars, cinnamon and nutmeg. Set aside. In a separate bowl, whisk together the flours, baking powder and salt.: As you toss, the pears begin to release juices, and you will see a glossy, spiced syrup coat the pieces, signaling that the fruit will infuse the batter with moisture and flavor. Whisking the dry ingredients separately ensures even distribution of the baking powder so the leavening works consistently. Avoid cutting the pears too small, which can cause them to disappear into the crumb, or too large, which can create heavy pockets; aim for uniform chunks for even texture.
In a large bowl, whisk together the sugar, eggs, milk, oil and applesauce. Whisk in the dry ingredients until they are just mixed in (don't over-mix). Stir in the pears and all of their sweet and spicy juices too. Divide the batter between the two pans. Bake 60 to 70 minutes, or until the loaves are baked through and test done (toothpick inserted in the centers comes out clean). Let the cakes cool for 15 minutes, then turn them out onto a rack to cool completely.: When you whisk these together, watch the mixture thicken slightly and the color lighten as air incorporates, creating a base that will trap bubbles for lift. The emulsion of eggs and liquid stabilizes the batter, while the oil and applesauce promise tenderness. Overbeating here is less risky than after adding flour, but keep a steady hand to avoid breaking the emulsion.
When cake is cool, prepare the icing. Melt the butter in a small saucepan over medium heat. Heat and stir for 5 to 7 minutes, or until the butter is lightly browned (you will see little flecks of brown throughout the melted butter when it is properly browned). Remove it from the stove and pour it into a bowl. Whisk in 1 cup of the powdered sugar. Add 3 teaspoons of the water and the vanilla. Whisk in more powdered sugar a little at a time until it thick but still pourable (add a teaspoon or two of additional water, if needed). Place paper towels under the rack and drizzle the icing onto the cakes. Serve immediately, or store in a covered container until ready to serve.: At this stage, the batter should come together with streaks disappearing but not beaten into a rubbery mass. You will see a smooth batter dotted with air bubbles, and that gentle incorporation keeps the crumb soft. Over-mixing activates gluten and yields a tough texture, so fold until the last streaks of flour vanish.
Stir in the pears and all of their sweet and spicy juices too.: As you fold the pears in, notice the batter take on flecks of spice and darker ribbons of pear syrup, creating a marbled, inviting appearance. The juices help keep the loaf moist as it bakes. Be careful not to overwork the batter here, or the fruit will break down and the batter can become overly wet.
Divide the batter between the two pans.: Pouring the batter reveals its weight and viscosity, and you should see an even fill that leaves room for rise. Tap the pans lightly on the counter to settle the batter and release large air pockets, which helps produce an even crumb. Filling pans unevenly will give you uneven baking times, so use a scale or visually match the batter levels.
Bake 60 to 70 minutes, or until the loaves are baked through and test done (toothpick inserted in the centers comes out clean).: During baking you will hear a faint crackle from the crust forming and smell the spices deepen into caramel aromas. The tops should become golden and slightly domed. Rely on the toothpick test rather than clock time alone, as ovens vary, and avoid opening the oven door frequently which can drop temperature and affect rise.
Let the cakes cool for 15 minutes, then turn them out onto a rack to cool completely.: Cooling allows the crumb to set so the loaf slices cleanly; you will feel the loaf firm slightly as steam releases. Turning out too soon can cause the cake to break apart, while leaving it longer in the pan may create condensation. Fifteen minutes strikes a balance, but if the loaves seem unstable, wait a bit longer to prevent tearing.
When cake is cool, prepare the icing.: The aroma of browning butter will fill the kitchen as the milk solids toast, offering a nutty, almost caramel scent that complements the pear and spice. Making the icing when the cake is cool prevents it from running off completely, giving you a glossy finish that clings to the top. If the butter browns too dark, it can taste burnt, so remove it from heat when you see tiny brown flecks and a nutty aroma.
Melt the butter in a small saucepan over medium heat. Heat and stir for 5 to 7 minutes, or until the butter is lightly browned (you will see little flecks of brown throughout the melted butter when it is properly browned).: You will hear gentle bubbling and see foam rise, and then small brown specks will appear as the milk solids caramelize. That nutty scent tells you the butter is ready. Keep stirring and monitor closely because the transition from browned to burnt is quick; if scorching begins, transfer the butter immediately to a cool bowl.
Remove it from the stove and pour it into a bowl. Whisk in 1 cup of the powdered sugar.: The hot butter will melt the sugar slightly, creating a thick paste that smooths as you whisk. This initial combination forms the body of the icing. If the powdered sugar lumps, press them against the bowl with your whisk to dissolve them completely before adding liquid.
Add 3 teaspoons of the water and the vanilla.: The boiling hot water helps dissolve remaining sugar quickly, making the glaze shine, while the vanilla lifts the flavor. You will see the mixture thin and become glossy as you whisk. Add the water slowly, because too much will make the icing overly runny and it will not set properly on the cake.
Whisk in more powdered sugar a little at a time until it thick but still pourable (add a teaspoon or two of additional water, if needed).: Aim for a ribbon like viscosity that drips slowly off a spoon and holds a soft sheen when it lands on the cake. The right balance yields a glossy drizzle that sets thinly but does not soak into the crumb. If the icing seems too thick, a single teaspoon of hot water is enough to loosen it without making it sheer.
Place paper towels under the rack and drizzle the icing onto the cakes.: Drizzling over a rack gives a tidy finish and allows excess to drip away onto paper towels, preventing puddles. The icing should form shiny ribbons and thin pools that cling to the top edges. Work quickly because the icing will start to set as it cools; slow movement can create uneven patches or a matte finish.
Serve immediately, or store in a covered container until ready to serve.: When you slice into a glazed loaf, you will notice a contrast between soft crumb and the slightly set glaze, which keeps the cake moist and visually appealing. Stored in a covered container, the loaves keep for several days at room temperature, but refrigeration will extend freshness if your kitchen is warm. If you refrigerate, allow slices to come to room temperature before serving for best texture.