Heat a skillet over medium heat and add a tablespoon of oil. Slice the onions and add them to the skillet. Cook, stirring occasionally, until caramelized, about 20-30 minutes.

In a mixing bowl, combine the sour cream, mayonnaise, caramelized onions, garlic powder, salt, and black pepper. Mix until well combined.

Transfer the dip to a serving bowl and garnish with chopped green onions. Serve with chips or vegetables.