1. Stir together first 10 ingredients in a large bowl until blended. Trim fat from steaks; add steaks to marinade, turning to coat. Cover and chill 8 hours, turning occasionally, or, if desired, let stand at room temperature up to 2 hours.
2. Remove steaks from marinade. Bring marinade to a boil in a small saucepan over medium heat, and boil 2 minutes.
3. Heat a grill pan coated with cooking spray over medium-high heat. Grill steaks 5 to 6 minutes on each side or to desired degree of doneness, basting occasionally with marinade.
4. Remove steaks from grill pan, and place on a serving plate. Dollop each with Guacamole Butter. Spoon Fiesta Black Bean Salsa around steaks, and serve immediately with remaining Guacamole Butter.