This sandwich holds up very well in a cooler and seems to get more flavorful after a couple of hours when the ingredients have melded together. Cut a big wedge, pour a glass of iced tea or lemonade and enjoy the day. If you’re short on time, buy the grilled vegetables from the salad bar of your supermarket.
Heat oven to 350 degrees F. Mix the brown sugar, cayenne and 1/8 teaspoon black pepper together and set aside. Cover a rimmed baking sheet with aluminum foil. Set a cooling rack in the pan and arrange bacon slices on it. Bake for 25 minutes, then remove pan from oven and flip the slices. Sprinkle with sugar and spice mixture; bake for another 15-20 minutes or until bacon is thoroughly cooked.
Heat grill to medium-high heat. Place whole red peppers on the grill. Cook for about 15 minutes, turning every five minutes, until skin is charred and peppers are softened. Brush zucchini, yellow squash and onion with oil and sprinkle with 1 teaspoon salt and a few grinds of pepper. Cook for 3-4 minutes per side or until vegetables are tender. When peppers have cooled, pull off most of the charred skin and cut each into 4 fillets.
For red-pepper aioli, put 3 of the red pepper fillets, mayonnaise, ketchup, mustard, hot sauce and garlic into a small food processor. Blend until peppers are pureed and ingredients are well mixed. Stir in capers.
To assemble sandwich, cut bread horizontally to leave a thinner bottom and thicker top. Pull out most of the soft dough in the top piece to make room for the fillings. Spread red-pepper aioli on inside of both pieces. On bottom piece, layer cheese, bacon and basil leaves. On the top half, arrange turkey; sprinkle with salt and pepper. Add remaining red pepper fillets, zucchini, squash and onion. Put the halves together. Wrap snugly in foil and press on the sandwich with your hands to encourage the ingredients to meld. When ready to serve, cut into 6 wedges.