The bacon in this lunchtime classic is baked with brown sugar and cayenne pepper.
Preheat oven to 400 degrees, with racks in upper and middle thirds. On a rimmed baking sheet, arrange bacon in a single layer and sprinkle with brown sugar and 1/2 teaspoon cayenne. On another rimmed baking sheet, toss tomatoes with oil and season with salt and pepper. Roast bacon on upper rack until crisp and tomatoes on middle rack until softened, about 15 minutes. Drain bacon on paper towels. Combine mayonnaise, jalapeno, and remaining 1/4 teaspoon cayenne and spread on bread. Assemble sandwiches with bread, bacon, tomatoes, and lettuce.
Roasting the tomatoes gives them a deep sweetness that holds its own with layers of smoke and spice.