Preheat oven to 325°F. Stir together chili powder, paprika, cayenne pepper, and 1/2 teaspoon each of the salt and black pepper; sprinkle over ribs. Heat 1 tablespoon of the oil in a Dutch oven over medium-high. Add ribs, and cook until browned on all sides, about 5 minutes. Remove ribs from Dutch oven; wipe Dutch oven clean.
Add remaining 1 tablespoon oil to Dutch oven. Add pearl onions; cook until lightly browned, about 4 minutes. Stir in flour, and cook, stirring constantly, 1 minute. Add beer, and bring to a boil, stirring and scraping to loosen browned bits from bottom of Dutch oven. Boil until liquid is reduced to about 1/2 cup, 3 to 4 minutes. Stir in tomatoes, broth, brown sugar, bay leaves, and 3/4 teaspoon of the salt. Add ribs, bone side up; bring to a boil. Cover and transfer to preheated oven. Bake until ribs are very tender, about 2 1/2 hours.
Prepare noodles according to package directions, and place in a medium bowl. Add butter, parsley, and remaining 1/4 teaspoon salt and 1/2 teaspoon black pepper, stirring until butter is melted.
Remove and discard bay leaves from Dutch oven. Serve ribs and onion mixture over noodles. Sprinkle with thyme.