Cover a cookie sheet with parchment paper, then place a roasting rack on top.
Cut 12 thick cut slices from medium-sized onions. You don't want the onion too big. You may need several medium onions in order to get 12 good slices. I used 3.
Wrap a piece of bacon around the onion barely overlapping so that the onion is covered but keeping as much of the bacon exposed as possible so that it will get nice and crispy. Sprinkle a little garlic powder on top.
Place on the middle rack in the oven and cook for 25 minutes then remove from onion and flip the onion rings over and bake for another 20 minutes.
Cook for 5 more minutes (more or less if you want crunchy or chewy).
Since every oven cooks a little different and each person may have a different preference for how they like their bacon. I recommend watching the Keto Onion Rings while cooking. Remove from oven when they reach the desired doneness.