Cook bacon on stovetop until crisp. Drain on absorbent paper. When the bacon is cool, coarsely chop it.
Arrange the tortilla chips on a large rimmed baking sheet. Scatter the bacon, onions, and jalapenos evenly over the chips. Sprinkle the grated cheese over all. Bake about 5 minutes, or until the cheese is melted and the nachos are sizzling (watch carefully to prevent overbrowning).
Serve immediately, accompanied by sour cream and salsa for dipping. (As the nachos already have jalapenos on them, choose a salsa that's not too hot).