Soak the squid: Place squid rings in buttermilk. Let them soak for 30–60 minutes.
Make the sauce: In a saucepan, heat olive oil. Add garlic and cook for 30 seconds. Add crushed tomatoes, oregano, salt, and pepper. Simmer for 10–15 minutes. Set aside.
Prepare coating: In a bowl, mix flour, cornstarch, salt, and paprika.
Heat oil: Heat oil in a deep pan to 350–375°F (175–190°C).
Coat and fry: Remove squid from buttermilk. Toss in flour mixture. Shake off excess. Fry in small batches for 2–3 minutes until golden.
Drain and serve: Place on paper towels to drain. Serve hot with lemon wedges and warm marinara sauce.