Start by preheating your oven to 425 degrees Fahrenheit to ensure it reaches a screaming hot temperature for optimal roasting. This high heat crisps the bacon perfectly and roasts the chicken to juicy perfection without drying it out. Lay out all your ingredients on a clean workspace to streamline the process, as efficiency keeps the kitchen stress-free during prep.

Position a wire rack over a baking sheet for the bacon; this setup allows drippings to fall away, preventing sogginess and mess on your stovetop. Gather your chicken breasts and pat them dry with paper towels if needed, promoting better adhesion for the spice rub. Having everything ready now avoids interruptions later when timings overlap.​

In a small bowl, combine 2 tsp dehydrated onion, 1 tsp smoked paprika, 1 tsp chili powder, 1-1/2 Tbsp brown sugar, 1/2 tsp dried mustard, and 1 tsp granulated garlic. Stir thoroughly with a spoon or fork until evenly mixed; this ensures the smoky barbecue flavor distributes consistently across the chicken. The brown sugar caramelizes slightly during roasting, adding a subtle sweetness that balances the spices.

Taste a tiny pinch if desired, but remember it packs punch, so no need for adjustments unless your palate prefers milder notes. This rub mimics barbecue sauce effects without stickiness, making it ideal for oven use. Set aside any extra rub in an airtight container; it stores well for weeks and works great on ribs, veggies, or steak.​

Generously sprinkle the spice rub on both sides of the 1 lb boneless skinless chicken breasts, pressing it in lightly for full coverage. Season with salt to taste, enhancing the flavors without overpowering. Finish with a drizzle of olive oil on both sides; this locks in moisture and helps the rub form a flavorful crust.

If using bone-in chicken for extra juiciness, adjust cooking time slightly longer, but boneless slices easier for sandwiches. Massage the rub gently to coat evenly, envisioning the smoky aroma filling your kitchen soon. Place seasoned chicken on a baking sheet or directly on the oven rack if lined properly.​

Slide the prepared chicken into the preheated 425-degree oven and set a timer for 30 minutes. The high heat roasts the chicken quickly, developing that coveted smoky char from the paprika and chili while the sugar creates caramelized edges. Rotate the tray halfway if your oven heats unevenly for uniform cooking.

Monitor internal temperature if possible, aiming for 165 degrees Fahrenheit at the thickest part to ensure safety without overcooking. As juices run clear and the exterior darkens to a beautiful mahogany, your kitchen fills with irresistible barbecue-like scents. Remove promptly at 30 minutes to rest.​

Ten minutes before the chicken finishes, place the 8 slices of thick maple glazed bacon on the wire rack over the baking sheet and slide into the oven alongside the chicken. The bacon crisps in just 10 minutes at 425 degrees, rendering fat perfectly while catching maple sweetness. In those same last 10 minutes, add your 8 slices of sourdough bread to the oven, drizzled lightly with olive oil on both sides for toasting.

Watch the bacon closely to avoid burning; it should be golden and rigid. The bread toasts to a crunchy texture that holds up against juicy fillings. This multi-tasking maximizes oven efficiency, saving time and energy.​

Remove everything from the oven: let chicken rest 5-10 minutes on a cutting board to redistribute juices, preventing dryness when sliced. The bacon drains excess fat on the rack for ultimate crispiness. Slice vine ripe tomatoes into even rounds and halve romaine leaves to fit sandwich size neatly.

Thinly slice rested chicken against the grain for tender, even pieces that stack beautifully. Press slightly on bacon to remove any lingering grease if needed. Toast ensures bread stays firm under moist layers.​

Spread Heinz mayonnaise generously on both slices of toasted sourdough; its creamy texture from cage-free eggs, lemon juice, and vinegars binds everything perfectly. Layer sliced chicken on the bottom slice, followed by tomato slices, romaine leaves, and 2 pieces of bacon per sandwich. Cap with top bread slice, mayo side down.

Press gently to compress layers without squishing. Cut diagonally for that classic sandwich look and even bites. Serve immediately for peak crunch and warmth.