Melt 1 tablespoon of the butter in a large skillet over medium heat. (Reserve 6 tablespoons to add to the dough and 1 tablespoon for brushing on the biscuits when they come out of the oven.) Add the onions and cook, stirring occasionally and keeping the heat on low, until golden brown, about 30 minutes. (Here’s the deal, you don’t have to cook them until golden, but you do need to cook them at least 5 minutes, just to get the excess moisture out.)
Once the onions are golden brown, transfer to a plate or bowl and pop them in the fridge or freezer to cool down slightly, about 5 minutes.
Meanwhile, heat the oven to 400°F. Line a baking sheet with parchment paper or a nonstick silicone baking sheet. Melt the reserved 6 tablespoons of butter.
Place the flour in a medium bowl. Add 1 cup of the cheese, herbs, and cayenne pepper; stir to combine. Add ¾ of the now-chilled golden brown onions, reserving a little for the Golden Onion Butter. (If you are skipping the butter, go ahead and add all the onions.) Add the melted butter and buttermilk and stir to combine.
Using a large scoop or a ¼-cup measure, spoon the batter onto the prepared baking sheet in a circle, leaving room for the bowl of butter in the center. Bake until lightly browned, about 15 minutes. Remove from the oven and top with remaining 1 cup of cheese. Return to the oven to finish cooking, about 5 more minutes.
While the biscuits are baking, combine the reserved ½ cup or so of onion and stick of room temperature butter. Add a little of the same herb that’s in the biscuit. Season with salt and pepper.
Slip the biscuit ring off onto a large platter or cutting board. Brush with last reserved tablespoon of butter. Pop the bowl of Golden Onion Butter in the center. Serve immediately. Swoon.