How to Make It
In a saucepan, cover the beans with 2 inches of water and bring to a boil. Simmer until tender, 40 minutes. Off the heat, stir in 1 1/2 teaspoons of salt. Let stand for 20 minutes, then drain and let cool.
In a bowl, toss the beans, celery, vinegar, and parsley with 1/4 cup of the olive oil. Season with salt and pepper.
Season the squid with salt. In a cast-iron skillet, heat the remaining 2 tablespoons of oil. In batches, cook the squid over high heat, stirring, until browned in spots, 2 minutes per batch.
Squeeze the lemon half over the beans and toss; mound on plates and top with the squid and lemon slices; serve.