Begin by placing a sauté pan on the stove over medium heat. Pour in the oil, and once it is hot enough, add in the onions and salt.
Next proceed to caramelise the onions. Keep the pan on low heat, and continue moving the onions around the pan with a wooden spoon, to keep them from browning too much on either side.
Once the onions become soft, golden and gooey, take them off the heat. The entire caramelisation process should take around 20 minutes, and once it is done, put the onions aside to cool.
Then, mix the olive oil, sour cream, mayonnaise, garlic powder, white pepper and salt together in a bowl. Add in the cooled onions, and mix it all together thoroughly. Have a taste, and adjust the seasonings if you feel it is needed.
Place the bowl in the refrigerator to cool, and when you take it out, give it a final mix before serving with a platter of potato chips, vegetable sticks, or whatever you may fancy.