Put the onion in a small bowl and pour in enough red-wine vinegar to cover well. Set aside for at least 30 minutes.

Combine the lettuce, tomatoes, and avocado in a serving bowl or platter. In a small bowl, whisk together 2 tablespoons of the red-wine vinegar from the marinating onion, 2 tablespoons of olive oil, and salt and pepper to taste. Set aside until you are ready to dress the salad.

Combine the ketchup, honey, chipotles, adobo sauce, and 1 teaspoon salt in a blender and purée. Set aside.

Preheat a grill to medium-high for 10 minutes or preheat a grill pan over medium-high heat. Brush the grill grates or grill pan with the remaining tablespoon of oil.

Season the beef on both sides with salt and pepper. Grill the meat for 4 minutes, turn over, and brush the glaze over the steak. Grill for another 4 minutes, turn over, and glaze the other side. Allow the meat to cook for another 2 minutes on each side to caramelize the glaze.

Remove from heat and allow the meat to rest for 5 minutes before slicing into ½-inch-wide strips. (This is for medium-rare beef. If you want your meat cooked longer, increase the time you grill the beef before adding the glaze.)

Pour the dressing over the lettuce mixture and toss well. Place the sliced beef over the salad and top with cheese crumbles and marinated red onions.