Soak the skewers in water for at least 1 hour, preferably 2 or 3.
To make the sauce, toast the chiles directly over a gas flame or in a castiron skillet until soft and brown, turning frequently to avoid scorching. Transfer the roasted chiles to a saucepan and add the water. Bring to a boil, reduce to a simmer and cook for 10 minutes, or until softened. Transfer the chiles and cooking water to a blender and puree until a smooth paste forms. Set aside. In a medium, heavy saucepan heat the oil over mediumhigh heat.
Saute the onion for about 8 minutes, stirring occasionally, until golden. Add the garlic and stir for a moment, just to release the aroma, then add the reserved chile paste, tomato, cumin, bay leaves, pepper, and salt. Reduce the heat to mediumlow and cook, partially covered, for about 20 minutes more, stirring occasionally. Return the sauce to the blender and blend again until smooth, adding a little more water if necessary to make the sauce move freely. Let cool.
Drain the skewers and make the brochettes by alternating cubes of beef, bell pepper, and red onion pieces. Leave 2 inches at the bottom of each skewer bare so that you will have room to grab and turn them. Heat a grill or griddle pan to high heat. Brush the skewers with a little olive oil and season to taste. Grill for 1 minute on each side, then brush generously with the sauce. Grill for another minute on each side, or until done to your liking. Spread a little of the sauce on each of 6 warm plates and serve a brochette in the center and a warm corn tortilla on the side. Pass the remaining sauce.
Note: To roast a tomato, heat a dry skillet or griddle over high heat. Roast the whole tomato, turning when the bottom is slightly charred, until it is golden brown with charred patches on all sides, but not burned (the flesh will be quite mushy). Leave the skin on.
c.1997, M.S. Milliken & S. Feniger, all rights reserved