In a large skillet or heavy-bottomed pan over medium heat, melt 4 tablespoons unsalted butter.

Add 4 chopped sweet onions and a big pinch of kosher salt and pepper (the recipe calls for at least 1/2 teaspoon of each total); stir to coat the onions in the butter.

Cook the onions 5 minutes, stirring occasionally, until they begin to soften.

Reduce the heat to low (or medium‑low if low isn’t cooking them). Continue to cook, stirring every 2–5 minutes, until the onions are deeply brown and caramelized, 30–60 minutes total. Watch carefully so they don’t burn; reduce the heat if they brown too quickly and scrape up any browned bits from the pan as you stir.

Remove the pan from the heat and let the onions cool for about 5–10 minutes so they won’t melt the dip base.

In a bowl, whisk together 1 cup sour cream (or plain Greek yogurt), 1/2 cup mayonnaise, and 1/2 teaspoon garlic powder. Season with kosher salt and pepper to taste—remember the recipe needs at least 1/2 teaspoon of each overall—and adjust as needed.

Stir the slightly cooled caramelized onions into the sour cream mixture until evenly combined. Taste and add more salt or pepper if desired.

Transfer the dip to a serving bowl, sprinkle with fresh herbs (like parsley), and serve immediately or refrigerate. The dip will thicken when chilled and will loosen slightly at room temperature. The onions can be caramelized a day or two ahead and gently reheated before mixing if you prefer warm onions.