Melt the butter in your Instant Pot using the sauté function. Add sliced onions, baking soda, salt, and pepper. Stir to combine. Continue cooking and stirring occasionally for another 5 minutes.

Put the lid on your Instant Pot, make sure the vent is set to "Sealing", and cook on high pressure for 16 minutes. When finished, quick release the pressure.

Remove lid and press the sauté button again. Stir constantly for 5 - 10 minutes until most of the liquid has evaporated. The onions will probably not be large discernable slices at this point, and the mixture should be dark brown.

At this point, I dump mine into a fine mesh sieve to strain the excess butter/liquid that is leftover. You *can* add it to the dip, but if there is a lot leftover your dip is going to be noticeably buttery.

Next, add the onions, sour cream, cream cheese, and soy sauce to a bowl. Mix well, then add salt & pepper to taste.

Refrigerate at least a few hours before serving. I like to make the day before and refrigerate overnight. This gives all the flavors a chance to meld together.