Heat olive oil in a large skillet over medium-high heat. Add the onions and kosher salt, and cook for 20 minutes, stirring occasionally, until the onions are light golden brown. Remove from heat and let them cool.

While the onions are cooling, combine the vegan sour cream, mayonnaise, vegan cream cheese, garlic powder, black pepper, and cayenne in a medium bowl. Stir until smooth and fully combined.

Once the onions have cooled, fold them into the creamy mixture. Stir until the onions are evenly distributed.

Refrigerate for at least 2 hours, but ideally overnight, to allow the flavors to meld.

Garnish with sliced scallions and serve cold or room temperature.