Preheat the oven to 450 degrees. Line a baking sheet with parchment paper coated with cooking spray.

Slice the onion into thick rings then separate them.

Pour the flour into a bowl and season it with a bit of sea salt and freshly cracked pepper, to taste, then mix well.

Mix the egg and milk in a bowl until well combined.

Pour the panko crumbs into another bowl.

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.

Spray the rings with cooking spray then place them into the oven.

Bake for 10 minutes then flip the rings over carefully with tongs.

Bake for an additional 10 minutes.

Remove from the oven and serve immediately. Enjoy.