Prepare a stove-top griddle or an outdoor grill.
In a medium bowl, combine the tomatoes, frisee, and capers. In a small bowl, whisk together 2 tablespoons olive oil, lime juice and zest, and salt and pepper. Drizzle over the frisee mixture and toss to coat.
Stuff 1 tablespoon of the frisee mixture into each squid. Brush the remaining teaspoon of olive oil on the squid.
Grill for 5 to 7 minutes, turning frequently.