This isn't a simple tuna salad. Instead of just mixing mayonnaise with tuna, you create a dynamic black olive pesto, which is spread on the bread right before it's grilled. The tuna is then spiked with capers, red wine vinegar, lemon juice, and red pepper flakes. It has flavor to spare. But the final trick that sends this sandwich over the edge is the panini press. Grilling the sandwich unifies it into one glorious, crispy package.