Pat the cleaned squid tubes and tentacles dry with paper towels. If tubes are whole, slice into 1/2-inch rings. Trim any excess cartilage. Place squid in a bowl and pour the buttermilk over it; toss to coat and let sit 10 minutes (this helps tenderize and helps coating adhere).

Make flour mixture

In a shallow bowl or rimmed plate, whisk together the all-purpose flour, cornstarch, salt, black pepper, paprika, and garlic powder until evenly combined.

Heat oil

Pour vegetable oil into a heavy-bottomed pot or deep fryer to a depth of about 2 inches (approx. 3–4 cups depending on vessel). Heat oil to 350°F (175°C). Use a thermometer for accuracy.

Dredge calamari

Working in batches of about 4–6 rings (do not overcrowd), remove squid from buttermilk letting excess drip off, then dredge thoroughly in the flour mixture, pressing lightly so the coating adheres. Shake off excess flour.

Fry

Carefully lower a single batch into the hot oil using a spider or slotted spoon. Fry until golden and crisp, 1.5 to 2 minutes. Remove with a slotted spoon or spider and transfer to a wire rack set over a sheet pan or paper towels to drain. Immediately season with a light pinch of salt.

Finish and serve

Repeat frying with remaining squid. Arrange fried calamari on a serving plate, sprinkle with chopped parsley, and place lemon wedges on the side. Serve hot with house cocktail sauce for dipping.

House Cocktail Sauce

In a small bowl, whisk together ketchup, prepared horseradish, fresh lemon juice, Worcestershire sauce, hot sauce, smoked paprika (if using), salt, and black pepper until smooth and well combined.

Taste and adjust seasoning: add more horseradish for heat, more lemon for brightness, or more hot sauce for spice. Refrigerate until ready to serve. Sauce can be made several hours ahead to let flavors meld.