This piquant open-face sandwich gets its kick from best-quality jarred salsa.
Heat broiler, with rack in top position. In a medium bowl, mix together tuna, salsa, and mayonnaise; season with salt and pepper. Cut baguette in half lengthwise and place, cut side up, on a rimmed baking sheet. Top with tuna mixture and pepper Jack cheese, and broil until cheese melts and begins to turn golden, 5 minutes. To serve, cut into pieces and sprinkle with parsley.