Step 1

Preheat oven to 375°F and grease a 1-qt baking dish.

Step 2

Cut onion into quarters and peel. Thinly slice three of the sections, then mince the last quarter.

Step 3

Add onions to bowl, along with mayonnaise, sour cream, cheeses, Worcestershire, garlic powder, and salt and pepper. Stir to combine.

Step 4

Transfer mixture to baking dish and bake until golden brown and bubbly, about 30 minutes.

Step 5

Serve with sliced, toasted baguette and enjoy!