Dice the onion. Using a nonstick sprayed skillet, cook sausage and onions until brown, stirring occasionally. Once browned, drain some of the fat from the skillet.
Cube Velveeta loaf. Add cubes to browned sausage and onion mixture. Add can of Rotel (juice and all), can of green chilies (juice and all), and stir over low heat.
Cut the top and bottom off the jalapeño, slice into matchsticks, then rotate and slice to create a fine dice. (For a spicy version, leave seeds and white membranes. For a milder option, remove them.) Add to queso and stir.
Serving tip: Use a fondue pot or crock pot to serve piping hot!