Slice the Vidalia onions into ¼" thick slices. Separate into rings and soak in the buttermilk for 1 hour.
In a large bowl or a large ziplock bag, combine ¾ cups of flour with the salt, pepper, garlic powder, and chili powder. Add the onions and toss to coat.
Add 3 inches of oil to a large, heavy-bottom pot and heat to 375°F.
In a large bowl, gently mix the beer into 1 cup of flour.
Remove the onions from the flour and shake off excess before coating in the beer batter.
Fry the onions in batches for 3 minutes. Place on a paper towel-lined plate and sprinkle with more salt. Let the oil get up to 375°F again before frying the next batch of onions.
Serve warm with your favorite dipping sauce.