It's a Barefoot Contessa recipe, Adam's cagy about the exact proportions, and I don't have the book — I had checked it out of the library a while ago, but wasn't all that impressed by it. But, I thought, how hard can it be?
Anyway, I winged it like so:
3 onions (I used 2 ½ white, ½ red, 'cause that's what I had on hand), roughly chopped and slowly fried 30 minutes with a knob of butter, a splash of olive oil, 1 tsp paprika, ½ tsp chili powder. (Adam says cayenne, but I didn't have any.) Fry until very soft and golden; and it really doesn't matter if some of them catch a bit.
Cool the onions down and mix with: 2 tbsp mayo, 2 heaped tbsp sour cream, 2 heaped tbsp cream cheese. Refrigerate overnight to let the flavours blend.
It came out good and it all went; I'd definitely make it again. Although next time I'd make two minor tweaks: chop the onions finer, and thin it a little with a splash of milk.
[Update: made it again with these tweaks for the 4th of July; good.]