In a shallow dish, mix together the flour, cornflour, salt, black pepper, garlic powder, paprika, dill, and cayenne pepper.
Pour vegetable oil into a heavy-bottomed pot, ensuring there’s enough oil to submerge the calamari rings. Heat the oil to 350°F.
Pour the buttermilk into another dish. Dip each calamari ring into the buttermilk, then flour, then buttermilk, then back into the flour mix, making sure it’s fully coated.
Carefully place the coated calamari rings into the hot oil. Fry the calamari in batches until they are golden brown and crispy, about 2-3 minutes per batch.