In a small bowl, combine the ancho powder with 1/4 cup of the cumin, 2 tablespoons of salt and 1/2 teaspoon of pepper. Set the ribs on a rimmed baking sheet and rub all over with the spice mix. Cover with plastic wrap and refrigerate for at least 2 hours or up to 10 hours.
Preheat the oven to 350°. Add 1/4 inch of water to the baking sheet and bake the ribs for 45 minutes, until barely tender. Cover with foil and bake until tender, about 30 minutes longer. Pour off the pan juices.
Meanwhile, in a blender, puree three-fourths of the jalapeños with the garlic and 1/2 cup of the lime juice. Blend in the honey and the remaining 1 tablespoon of cumin. Transfer the glaze to a saucepan and simmer over low heat until glossy and thickened, 15 minutes.
Raise the oven temperature to 450°. Brush the ribs with half of the glaze. Roast until well glazed, turning once, about 20 minutes. Brush with the remaining glaze.
Light a grill or preheat the broiler. Grill the pineapple rings over high heat, turning once, until lightly charred, about 5 minutes. Finely dice the pineapple and transfer to a bowl. Add the brown sugar, onion, cilantro, avocado and remaining jalapeño and 2 tablespoons of lime juice. Season with salt and pepper.
Grill or broil the ribs over high heat, turning once, until caramelized, about 5 minutes. Cut between the bones and serve with the salsa.