Ready In. 1  Mix the brown sugar, fajita seasoning, and paprika in a bowl. 2  Preheat an oven to 250 degrees F (120 degrees C). 3  Tear off 2 large sheets of heavy duty aluminum foil and lay them shiny-side down. 4  Bake in the preheated oven until the ribs are very tender, 3 hours and 30 minutes to 4 hours. 5  Preheat the oven's broiler and set the oven rack ...