Slice the cleaned squid tubes into rings. Place the calamari and shrimp into a large bowl and pour over the buttermilk or cream. Add the onion powder, garlic powder, salt, and pepper. Stir gently and set aside to soak.
In a large mixing bowl, whisk together the flour, onion powder, paprika, cracked pepper, and kosher salt.
Arrange your dipping station: soaked seafood, seasoned flour, and a large platter lined with paper towels for draining.
In a heavy-bottomed pot, heat the oil over medium heat to 350°F. If you don’t have a thermometer, the oil should shimmer and ripple slightly but not smoke. If it begins to smoke, remove it from the heat to cool briefly.
Dip each piece of squid and shrimp into the seasoned flour, shaking off the excess. Carefully place the pieces into the hot oil. The oil should bubble immediately. Fill the pan without overcrowding.
Fry for 5 to 7 minutes or until golden brown. Transfer cooked seafood to the paper towel-lined platter and immediately sprinkle with sea salt.
After all seafood is fried, add the thin lemon slices and fresh herbs to the oil. Fry for 3 to 4 minutes until crispy.
In a food processor, combine all aioli ingredients and pulse until smooth and creamy. Refrigerate until ready to serve. The aioli will keep in the fridge for up to 4 days.
Serve the hot fritto misto with crispy lemon slices, fried herbs, and a generous side of garlic and herb aioli for dipping.