Peel the onion and slice off the top and bottom of the onion. Cut the onion into 1/4 inch slices and then separate each slice into the individual rings.
Mix together the flour, baking powder, and seasoning salt.
Take each onion ring and dredge it in the flour mixture and then set it aside.
To the leftover flour mixture, add the egg and 3/4 of the cup of milk. Mix well with a whisk and add more of the milk until you end up with batter with the consistency of a thin pancake batter. When you scoop it up on a fork, it will drip through the tines. Set aside.
Get a cookie sheet and line it with parchment paper. Then, get a cooling rack and set it on the parchment paper lined cookie sheet.
Get a shallow dish and add the panko crumbs, granulated garlic, salt and cayenne. Mix well.
Take each dredged onion ring and coat it in the batter and then lay it on the cooling rack to drip off a bit. Once you have battered all of the rings, take each ring and coat it in the panko mixture and place it on a plate.
Heat the deep fryer to 350 F and once it is up to temperature, take a couple of onion rings and fry them up to assess the temp of the oil and the length of time to get the onion rings nice and golden brown.
Proceed to fry the onion rings in batches. It should only take a few minutes per batch. Once the batch is done, empty it out into a bowl and add salt immediately. Complete the batches and serve immediately! Enjoy.
The calorie count does not include the fat from frying the rings as I was unsure how much oil actually stays with the onion rings.