Soften cream cheese. Make sure it is completely softened - defrost in microwave if needed.
Melt butter in a large skillet under medium heat, then add diced onions. Stir every 30 seconds or so to make sure onions are evenly cooked. Sauté until onions are soft and golden brown. This may take a little while - be patient! Add a pinch of salt to open up flavors. Remove from heat.
In a large bowl, combine sour cream, softened cream cheese, caramelized diced onions, sugar, soy sauce, and 1/2 tsp salt (see Note 1). Mix well.
Optional: garnish with chopped green onions.
Serve and enjoy!
Note 1: Adjust salt accordingly! If you like it less salty, taste before adding salt as you may not need the amount the recipe calls for!