In a medium skillet, cook the chorizo over medium heat, breaking it up as it cooks, until completely browned. Remove with a slotted spoon to a paper towel-lined plate to drain.
Pour off all but 1 tablespoon of the grease and add the onion and jalapeños to the pan and cook over medium heat until softened, about 5 minutes. Remove from the heat and add the sausage back to the pan, stirring to combine with the onion mixture.
In an 8-inch cast iron skillet, place ¼ of the shredded cheese, then layer with one-third of of the sausage mixture. Repeat twice more, then top with the remaining shredded cheese. Place in the oven and bake until the cheese is completely melted and bubbly. (Be careful not to over-bake, as the cheese will become firm on top and it will be difficult to scoop it out with chips!) Sprinkle with cilantro and serve immediately with your favorite tortilla chips.