Add the garlic, chipotle, citrus juices, red onion, mustard seeds to a blender or mini-food processor. With the machine running gradually drizzle in the oil until the desired creamy texture is achieved. You may not need all the oil. Gradually whisk in oil until blended. Set aside until ready to serve.
Soak the calamari in the buttermilk for at least one hour. Combine the flour with the parsley, salt, pepper and cayenne in a medium bowl. Remove the calamari from the buttermilk and shake off a bit of the excess. Dredge the calamari in the flour mixture, keeping all the pieces separate. Shake off the excess flour.
Pour oil to a depth of about 2 inches in a deep pan. Heat to 365. Fry calamari, in batches, for about 1 minute or until done, turning after 30 seconds. Make sure to not crowd the pan. Drain on paper towels, season with salt and a big spritz of lemon. Serve with additional fresh squeezed lemon, and some of the Chipotle sauce on the side.