If using chuck roast, pulse the freezer-firmed meat in a food processor to a coarse ground beef texture. In a very large skillet set over medium-high, cook onions until golden brown but still crunchy, about 4 to 5 minutes. Add the ground beef, spreading it over the entire surface to ensure even browning. Sprinkle in the chile powders, oregano, cumin and black pepper. Mix everything together and cook for another 4 to 5 minutes, until the meat is cooked through. Taste and season with salt and a big pinch sugar to give the classic American chile powder flavor. Remove from the heat.
Sprinkle in about 1/2 cup of the jack cheese to the skillet and mix just to incorporate. To make each taco lay a corn tortilla on a plate and spoon on a portion of the meat, sour cream, the remaining Jack cheese, lettuce, tomato and hot sauce. Serve immediately.