Melt the butter in a large saute pan over medium-high heat. Add the red onions, garlic and salt and cook until translucent. Add the mustard powder, cayenne and hot sauce and mix well.
Reduce the heat to medium and add the cream cheese. Cook, mixing occasionally, until melted.
Add the sour cream, Pimento Cheese Spread and red wine vinegar and mix until everything is heated through.
Transfer to a warmer for serving.
Arrange the toppings in small bowls so you can top you dip as you like.
Place the drained pimientos in a blender or food processor and puree until smooth. Using an electric mixer, combine the pimentos and cheese, beating until smooth. Beat in the mayonnaise.