Step 1

Combine salt and sugar in bowl. Place turkey on counter breast side down. Using kitchen shears, cut through bones on either side of backbone, staying as close as possible to backbone. Remove backbone and save for gravy, if making. Flip turkey over and press down firmly with heels of your hands to flatten breastbone.

Step 2

Using your fingers, carefully loosen skin covering breast and leg quarters. Rub 5 teaspoons salt mixture under skin of each side of breast, 2 teaspoons under skin of each leg, and remaining mixture onto cavity. Tuck wings under turkey and place turkey skin side up on wire rack set in rimmed baking sheet. Refrigerate, uncovered, for at least 24 hours or up to 2 days.

Step 3

Adjust oven racks to upper-middle and lower-middle positions and heat oven to 250 degrees. Spread bread cubes in even layer on 2 rimmed baking sheets and bake until mostly dry and very lightly browned, 40 to 50 minutes, stirring halfway through baking. Remove bread from oven and cool on sheets for at least 15 minutes.

Step 4

While bread cools, adjust lower oven rack to middle position and increase oven temperature to 425 degrees. Whisk eggs and water in large bowl until combined. When bread is cool, add to egg mixture and toss gently so bread is fully coated but does not break apart; set aside.

Step 5

Melt 4 tablespoons butter in 12-inch nonstick skillet over medium heat. Add onions and celery and cook, stirring occasionally, until softened, 8 to 10 minutes. Stir in thyme, sage, garlic, and pepper and cook until fragrant, about 30 seconds. Transfer vegetables to bowl with bread and stir gently to combine (stuffing will seem dry). (Stuffing can be refrigerated for 24 hours.)

Step 6

Spray roasting pan with vegetable oil spray. Transfer stuffing to pan and shape into level 9 by 9-inch square. Pat turkey dry with paper towels. Arrange turkey on top of stuffing. Tuck any exposed stuffing under bird, so all of stuffing is covered. Cover breast with double layer of aluminum foil. Roast on middle rack for 45 minutes. Remove turkey from oven and discard foil.

Step 7

Reduce oven temperature to 325 degrees. Melt remaining 1 tablespoon butter and brush evenly over turkey. Return turkey to oven and continue to roast until skin is deep golden brown and breast registers 155 degrees and thighs register 175 degrees, 2 to 2½ hours longer.

Step 8

Transfer turkey to carving board and let rest, uncovered, for 30 minutes. While turkey rests, stir stuffing well to incorporate drippings and scrape up any browned bits. Redistribute stuffing over bottom of roasting pan in even layer. When turkey has rested for 15 minutes, return stuffing to oven and bake until golden brown, about 15 minutes. Transfer stuffing to serving dish. Carve turkey and arrange on serving platter. Serve turkey with stuffing.