Peel the onion. Slice the onion into thin slices (but not too thin, otherwise they will be flimsy break and difficult to handle). Separate the onion rounds for the onion rings.
Whisk together the flour and water. Set aside.
In a separate bowl, mix together the ingredients for the seasoned breadcrumbs. When using the breadcrumbs, take batches of prepared breadcrumbs at a time into a separate bowl to use in order to avoid ending up with a clumpy breadcrumb bowl (due to dipping the flour coated onion rings into the breadcrumb mixture).
Lightly spray a baking pan with olive oil. I prefer to bake directly on the tray for these onion rings, but you can just as easily line the baking tray with parchment paper prior to baking and spraying. (see notes below)
Line the onions, flour/water batter mixture, and seasoned breadcrumb bowls next to each other and next to the prepared baking tray.
Whisk the batter once more prior to starting. One by one, place each onion ring in the flour batter and coat well, then place into the seasoned breadcrumbs and coat well all around. If you find that your breadcrumbs start to get clumpy, feel free to replace them with fresh ones. Place the prepared onion ring on the prepared tray.
Once the tray is filled, lightly spray some olive oil on top of the onion rings.
Place the tray in the preheated oven and bake for about 6 minutes.
Carefully flip each onion ring, and bake once again for 2-3 minutes until crispy and slightly browned (but not burnt). Note that ovens may vary, and since baking time is short, watch the onion rings frequently to ensure they do not burn.
Olive Oil Spray - I prefer to use olive oil spray for a lot of my baking and cooking to minimize the amount of oil when baking. Most of the times you do not need that much, if any at all. If you do not have olive oil spray, you can simply lightly brush olive oil on the entire pan prior to placing the coated onion rings, and then lightly brush the top of the onion rings as well prior to placing them in the oven.Baking - I also prefer to bake directly on the tray for these onion rings, but you can line the baking tray with parchment paper as well.For Gluten-Free Option - Use gluten-free flour and breadcrumbs.