Heat grill. Wrap tortillas in foil; set aside. In medium bowl, combine tomato, onion, cilantro and salt; mix well. Set aside.
When ready to grill, place bratwurst on gas grill over medium heat or on charcoal grill 4 to 6 inches from medium coals. Cook 5 to 8 minutes or until bratwurst is thoroughly heated, turning frequently.
During last 3 to 4 minutes of cooking time, place tortilla packet on grill; heat until tortillas are warm, turning foil packet once.
For each serving, stack 2 tortillas; place 1 grilled bratwurst on each tortilla stack. Top with tomato mixture, guacamole and sour cream.