In a small saucepan combine ancho pepper, lime juice, and 2 tablespoons water; cook on low heat, covered, for 10 minutes or until pepper turns soft. Drain and cool. Remove stem and seeds of pepper. Finely chop pepper and combine with softened butter or margarine.
Slightly mash the avocado with the salt. Stir into butter. Cover and chill or spoon into small mold or cup lined with plastic wrap; chill.
Remove husks and silk from ears of corn. If desired, leave a few leaves of the husks intact for presentation. In a large saucepan cook corn, covered, in a small amount of boiling water for 5 to 7 minutes. Drain. Grill on an uncovered grill directly over medium coals for 10 minutes, turning serveral times. Remove butter from mold. Remove plastic wrap. Serve corn with ancho-avocado butter.