from The Barefoot Contessa Cookbook

Once you taste this, you'll never eat dip made from instant onion soup mix again! Makes two cups. Recipe can easily be halved or doubled.

2 large yellow onions
4 T unsalted butter
¼ c vegetable oil
¼ tsp ground cayenne pepper [I use a bit less]
1 tsp kosher salt
½ tsp freshly ground black pepper
4 oz cream cheese, room temperature
½ c sour cream
½ c Hellman's mayonnaise