Alton Brown's Onion Dip

I'm in charge of appetizers for Thanksgiving this year and I was asked to keep it low-brow. While I admit that I dropped more than a small chunk of change on predictable junk like chips and crackers, I "forgot" to pick up dip packets to make sour cream-based dips. So, I looked up a few.
This one comes to you courtesy of Alton Brown, who is about the smartest food person I know. (OK, I don't really know him. We've never met. But in an alternate universe, we are friends and I can call him up whenever I have a cooking question.) It got rave reviews on FoodNetwork.com. And, I think I may never buy an onion dip packet again (not that I make a habit of it anyhow). It takes minimal effort except for dicing up two onions, which is quick work with my handy-dandy mandolin. All credit goes to Alton Brown on this one. I have not altered any ingredients (although I do think there is no such thing as too many caramelized onions).

Alton Brown’s Onion Dip

2 tablespoons olive oil
1 1/2 cups diced onions
1/4 teaspoon kosher salt
1 1/2 cups sour cream
3/4 cup mayonnaise
1/4 teaspoon garlic powder
1/4 teaspoon ground white pepper
1/2 teaspoon kosher salt

In a saute pan over medium heat add oil, heat and add onions and salt. Cook the onions until they are caramelized, about 20 minutes. Remove from heat and set aside to cool. Mix the rest of the ingredients, and then add the cooled onions. Refrigerate and stir again before serving.

Substitution Suggestions: I honestly can't think of any (unless you only have table salt, which will work). I read one review in which the reviewer omitted the onions (why?!) and added chopped dill instead. I guess that would work, but this is all about the caramelized onion.

Lessons Learned: I kind of wish I'd diced another onion. As it is, I diced two Vidalia onions for a yield of just shy of two cups. I also upped the amount of garlic powder and decreased the amount of mayo to 1/2 cup.
This is not a recipe you throw together 10 minutes before you need it. It needs time to get happy (to borrow an Emeril phrase). Let the flavors meld overnight and it'll be fully ready to serve.