01 - Place calamari rings and tentacles in a bowl with buttermilk, salt, and black pepper. Toss well to coat, cover, and refrigerate for 15 minutes.
02 - Heat olive oil in a saucepan over medium heat. Add onion and cook until soft, about 3 minutes. Add garlic and sauté for 30 seconds until fragrant.
03 - Pour in crushed tomatoes, oregano, red pepper flakes (if using), sugar, salt, and black pepper. Simmer for 10-12 minutes, stirring occasionally, until slightly thickened.
04 - Stir in basil and adjust seasoning as needed. Keep warm while preparing calamari.
05 - In a shallow bowl, whisk together flour, cornmeal, paprika, cayenne (if using), and garlic powder until well combined.
06 - Heat vegetable oil in a deep pan or fryer to 350°F.
07 - Remove calamari from marinade, shake off excess buttermilk, and dredge in flour mixture until well coated on all sides.
08 - Fry calamari in batches for 1-2 minutes until golden and crisp. Do not overcrowd the pan to maintain proper oil temperature.
09 - Remove with a slotted spoon and drain on paper towels. Serve immediately with warm marinara sauce, lemon wedges, and a sprinkle of parsley if desired.