Slice the onion into thick rings, then separate them.
Make a dredging station by pouring the flour into a shallow bowl and seasoning it with garlic powder, sea salt, freshly cracked black pepper, and crushed red pepper flakes to taste, then mix well.
Whisk the egg and milk in a shallow bowl, and season with garlic powder, sea salt, freshly cracked black pepper, and crushed red pepper flakes to taste, until well combined.
Pour the panko crumbs into a separate shallow bowl, and season with garlic powder, sea salt, freshly cracked black pepper, and crushed red pepper flakes to taste, until well combined.
Dredge the onions first in the flour, then in the egg mixture, and finally in the panko crumbs until fully coated.
Place each coated ring on the baking sheet. Repeat with the remaining rings.
Place the baking sheet in the fridge for 15 minutes. Side Note: Don't skip this step! It helps the panko stay adhered to the onion rings while baking.
Preheat the oven to 450 degrees.
Spray the rings well with olive oil cooking spray.
Bake the onion rings by placing the baking sheet in the oven to bake for 10 minutes.
Flip the rings over carefully with tongs.
Bake for an additional 7-10 minutes, or until golden brown and crispy.
Make the sauce by combining the mayonnaise, ketchup, and dill pickle juice until smooth.
Remove from the oven and serve immediately. Enjoy.