Set up three shallow bowls. In the first bowl, add the flour. In the second bowl, mix the cornmeal, lemon zest, dried dill, garlic powder, onion powder, salt, and black pepper. In the third bowl, whisk together the beaten egg and milk.

Take each fish cube and dip it first into the flour, shaking off the excess. Next, dip it into the egg mixture, allowing the extra to drip off, and finally coat it in the cornmeal mixture, pressing gently to ensure it sticks.

In a large skillet, heat about ½ inch of oil over medium-high heat until it shimmers.

Carefully add the coated fish bites to the hot oil in batches, making sure not to overcrowd the skillet. Fry for about 3-4 minutes on each side or until golden brown and cooked through. Use a slotted spoon to transfer the cooked fish bites to a paper towel-lined plate to drain excess oil.

In a small bowl, combine the mayonnaise, dill pickle relish, lemon juice, dried dill, salt, and pepper. Stir until smooth and well combined.

Refrigerate the tartar sauce for at least 15 minutes to allow the flavors to meld. For an extra kick, feel free to add a pinch of cayenne pepper to the cornmeal mixture.