For the Steak: Stir together tequila, lime rind and next 8 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.
Remove steaks from marinade. Bring marinade to a boil in a small saucepan over medium heat and boil 2 minutes.
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.
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.
For the Guacamole Butter: Peel and coarsely chop small avocado, discarding pit.
Process avocado, chopped green onions and remaining ingredients in a food processor or blender until smooth, stopping to scrape down sides. Place mixture in a bowl; cover and chill until ready to serve.
For the Fiesta Black Bean Salsa: Stir together all ingredients in a large bowl. Cover and let stand at room temperature until ready to serve.