01 - Combine calamari rings with buttermilk and ½ teaspoon salt in a bowl. Toss to coat evenly and refrigerate for 15 to 20 minutes.
02 - In a shallow dish, blend flour, cornmeal, paprika, black pepper, garlic powder, and ½ teaspoon salt until well combined.
03 - Heat vegetable oil to 350°F (180°C) in a deep fryer or heavy pot.
04 - Warm olive oil over medium heat in a small saucepan. Sauté minced garlic until fragrant, about 1 minute. Add crushed tomatoes, oregano, red pepper flakes, sugar, and season with salt and pepper. Simmer for 10 minutes, stirring occasionally. Stir in fresh basil if using. Keep warm.
05 - Remove calamari from buttermilk, allowing excess to drain. Coat thoroughly with the flour and cornmeal mixture.
06 - Fry calamari in batches in hot oil without overcrowding, cooking 1½ to 2 minutes until golden and crisp. Remove with a slotted spoon and drain on paper towels.
07 - Plate calamari hot, accompanied by marinara sauce and garnished with lemon wedges and chopped parsley.