Place calamari in a bowl, drizzle lemon juice over, stir gently, and let sit for 30 minutes to tenderize.
Organize three bowls: One with the seasoned flour (mix flour + cayenne + paprika + salt), one with buttermilk (or milk), and a second bowl with more of the seasoned flour.
Remove calamari from the lemon juice. Dredge each piece first in flour, shake off excess, then in buttermilk, then again in flour. Do this for all pieces.
Heat oil in deep fryer or large pot to 375°F (fill no more than half full).
Fry calamari in batches for about 3 minutes total per batch, until golden‑brown. Avoid overcrowding.
Drain the fried calamari on paper towels; while still hot, sprinkle with salt so it adheres.
Serve immediately with lemon wedges and choice of dipping sauce (marinara or aioli).