In a medium bowl, mix together the mayonnaise
and the lemon juice
. Add the tuna, salt, and pepper, and stir to combine.
Cut the focaccia
in half and brush the outside of the bread with olive oil. Place a slice of cheese on the bottom half of the panino
. Top with tuna mixture, then the frisee, and then another slice of cheese. Finish with the top half of the focaccia.
Preheat a panino grill, or heat a grill pan
over medium heat. Drizzle
with olive oil to prevent sticking. Grill the panino until the cheese melts and the bread is crisp
and golden, about 5 minutes. Cut the panino in half and serve.