Cut the tomatoes into small pieces, dice the onions. Fry the mince in the pan until crumbly and season with salt and pepper.
Spread half of the nachos on the bottom of a flat ovenproof dish, spread half of the fried mince, half of the tomatoes, onions and jalapeños on top, pour half of the sauce over it and sprinkle with half of the cheese. Layer like this until everything is used up.
Baked in the oven or in a closed grill, depending on your taste, until the cheese has melted. Serve hot.