For the Onion:
1 large Vidalia onion
2 cups lowfat buttermilk, or to cover
⅔ cup panko breadcrumbs
¼ cup regular breadcrumbs (seasoned or unseasoned)
1 tablespoon Cajun seasoning
¼ teaspoon salt
Nonstick baking spray
For the Dip:
½ cup Greek yogurt
2 tablespoons ketchup
1 tablespoon creamy horseradish sauce
¼ teaspoon smoked paprika
¼ teaspoon salt

1 large Vidalia onion 2 cup s lowfat buttermilk, or to cover 1 tablespoon Cajun seasoning 2 tablespoons ketchup 1 tablespoon creamy horseradish sauce

Use a knife to cut off the top ¼ inch of the onion. Leave the root intact. Peel the outside layer of the onion down all the way to the root and peel it off.
Then, create the sections that will form the petals. To do this, slice the onion from the top down to about ⅛ of an inch from the root. Then halve that, and repeat until there are 8 to 16 sections.
Once all of the cuts have been completed, you can use your fingers to spread apart the petals and open up the onion. If any of the cuts didn't go completely through, simply push down gently and they should separate.
Then, carefully transfer the onion to a bowl that is big enough to fit the entire onion in. Pour in the buttermilk, making sure that it gets in between all of the petals. Cover it and let it sit in the refrigerator for 1-2 hours.
After the 1-2 hours, whisk together the Panko bread crumbs, regular bread crumbs, Cajun seasoning, and salt in a separate bowl.
Preheat the oven to 375 degrees. Line a baking sheet with parchment paper.
Remove the onion from the buttermilk bowl and place it upside-down in a strainer. Let the excess buttermilk drip off. If there are still globs of thick buttermilk stuck between the petals, dab them to remove some of the excess if necessary. The onion should not be dry, but you don't want pools of buttermilk resting on the inside or else your breadcrumbs will stay mushy.
Reopen the petals and pour bread crumbs onto the soaked onion to coat well. Make sure you have gotten in between each of the petals and have a generous amount of the breadcrumb mixture on each. Place the onion onto a baking sheet. Lightly spray the entire onion with nonstick spray and put it in the oven for about 18 minutes, or until golden brown.
As the onion bakes, mix together all of the dipping sauce ingredients.
When the onion is finished baking, let it cool, and then top with some of the dipping sauce or serve the sauce on the side.