Line a large, rimmed baking sheet pan with a double layer of foil, and spray the foil with non-stick spray.
Pat ribs dry and lay racks on the baking sheet pan.
In a small bowl, whisk together brown sugar, smoked paprika, kosher salt, chipotle chili powder, cumin, allspice, and black peper.
Rub ribs with spice mixture and marinate, meaty sides up, covered and chilled, 2-½ hours.
Bring ribs to room temperature, about 30 minutes.
Put oven rack in middle position and preheat oven to 350 degrees F.
Cover pan tightly with foil; bake 1 hour and 15 minutes. Remove foil.
Make sauce while ribs bake: