Preheat your oven to 400° and line a rimmed sheet pan with parchment or silicon baking mat.
Place the onion petals, flour, bread crumbs and egg whites in separate bowls. Divide the spices among the flour and the breadcrumbs, so that's 2 teaspoons of the all purpose seasoning, 1/2 teaspoon of garlic powder, 1/4 teaspoon black pepper and 1/8 teaspoon of cayenne in both bowls and mix to combine.
Dip the onion petals in the flour and shake off the excess. Dip the petals into the egg whites and let the extra whites drip off.
Then place the flour and egg coated onions into the seasoned breadcrumbs and toss to coat.
Place the breaded onions onto the prepared sheet pan and repeat with the remaining onions.
Bake in your preheated oven for 18-20 minutes, rotating the pan halfway through baking.
Serve immediately with the fry sauce and start dipping.
MAKE THE FRY SAUCE:
Combine 2/3 cup mayo and 1/3 cup ketchup, mix until smooth, cover and store in the fridge until you're ready to serve.