Heat the oil in a very large (12-inch) skillet over medium-high. Add the tomato, onion and chiles, and cook, stirring nearly constantly, until the onion begins to soften and brown, about 7 minutes. Add the tequila and cook quickly, stirring, until nearly reduced to a glaze. (If you tip the pan toward an open gas flame, it will ignite. If you choose this route, simply shake the pan back and forth until the flames subside and the tequila has reduced to a glaze.)
Reduce the heat to medium-low, sprinkle the cheese evenly over the vegetables and stir slowly and constantly until just melted—too long over the heat and the cheese will become tough, oily and stringy.
Scoop into a warm dish, sprinkle with the cilantro and serve right away with tortillas for making soft tacos. You may want a little salsa, too.
How do you get a sterno to fit underneath? I have not found one small enough to fit in the bracket that is supposed to hold it. What to do?
Try sliding a tea light or two underneath a small fondue dish. That should keep it plenty warm.