Preheat oven to 425°F. Line a large sheet pan with foil. Pat chicken thighs completely dry with paper towels. No need to trim excess fat; it will render as the chicken cooks.
In a small bowl, whisk together olive oil, balsamic vinegar, ancho chili powder, oregano cumin, garlic powder, and paprika. Season to taste (I add 2 teaspoon salt & 1-1/2 teaspoon pepper). Rub or brush the seasoning mixture over the back first, and then the front of each thigh until evenly coated. You should use all the spice mixture.
Arrange chicken thighs flat on the prepared sheet pan, spaced out well. Bake in the center of the oven for 15 minutes.
Move the oven rack to 8 inches from the heat source. Switch to broil and cook for 7–10 minutes, or until the tops are nicely blackened and caramelized (watch closely).
Remove from oven, tent with foil, and let rest for 5–10 minutes. Brush pan juices on top. Drizzle generously with fresh lime juice. Slice or chop as desired.
Video
Notes
Note 1: Choose chicken thighs that are similar in size for the most even cooking. Weigh them if possible to get as close to 2 pounds as you can. I typically use 6 thighs. If yours are larger, the bake time may need to be slightly longer.Note 2: Use regular chili powder if needed, but it will be a bit spicier. Ancho chili powder is just ground dried poblano peppers so it has a mild, sweet, smoky flavor.Storage: Store leftovers in an airtight container in the fridge for up to 5 days or freeze for up to 2 months.