Melt the butter in a large skillet or saute pan over medium-high heat.
Add the red onions, jalapenos and salt and cook until the onions are soft and translucent, 5 minutes.
Add the artichokes and cook until starting to fall apart, 8 to 10 minutes.
Reduce the heat to medium and add the cream cheese, stirring until melted.
Add the sour cream and Jack cheese and mix until well combined.
Transfer the dip to a warmer or slow cooker to hold for serving.