Pour buttermilk into a large bowl.
Put flour in another large bowl.
Season flour with salt and pepper.
Pour oil into a large, heavy saucepan. Heat oil to 375 degrees F.
Cut the squid into 1/2-inch rings, leaving the tentacles intact.
Working in batches, dip a few calamari pieces at a time in the buttermilk, coating thoroughly. Remove from buttermilk and dredge in flour. Shake off excess flour.
Add the battered calamari to saucepan. Fry about 1 minute, or until golden brown.
Transfer calamari to paper towels with a slotted spoon.
Repeat process with remaining calamari, buttermilk and flour.
Serve with lemon wedges or a simple marinara sauce.