Trim the pork of any silverskin and excess fat, and cut each tenderloin on the diagonal into four pieces about 2 inches thick. Turn the pieces so that they’re lying on a cut side, and using a meat mallet, a small heavy skillet, or the heel of your hand, lightly pound the steaks so they’re about 1/2 inch thick.
In a small bowl, mix the chili powder, cumin, brown sugar, garlic powder, 2 tsp. salt, and 1 tsp. black pepper. Rub this spice mixture all over the pork and let it sit for at least 15 minutes at room temperature or refrigerate for up to 2 hours.
Heat a gas grill to medium-high or prepare a medium charcoal fire. When the grill is ready, cook the pork, covered, until it forms nice grill marks, about 3 minutes. Flip and continue cooking until just firm to the touch but still a little pink in the center (an instantread thermometer inserted into the center of each steak should register 140°F), 3 to 4 more minutes.
Transfer the pork to a large serving platter and let rest, tented with aluminum foil. Meanwhile, stir together the honey, vinegar, tomato paste, chipotle and adobo sauce, and mustard, and season with salt and pepper to taste. Spoon the sauce over the pork.
These steaks are delicious with roasted sweet potato wedges seasoned with salt, pepper, and a little chili powder.