1. Heat oven to 325 degrees. For crust, mix butter, graham crackers, sugar and cinnamon in medium bowl. Pat onto bottom and sides of 9-inch pie pan. Bake 8 minutes. Set aside; let cool completely.
2. For filling, beat yolks in food processor fitted with metal blade or with hand mixer, about 2 minutes. Add condensed milk to yolks; process or beat until incorporated. Add lime juice. Process 2 minutes; pour into pie shell. Bake until set, 10 to 15 minutes. Remove from oven; cool on wire rack 1 hour. Refrigerate, covered with plastic wrap set directly on top of curd, at least 3 hours or overnight. Top with fresh whipped cream.
Note: Instead of whipped cream, you may top with meringue: Beat 5 egg whites until stiff but not dry. Add 1/ 4 cup sugar, beating constantly until combined. Spread over baked filling; bake at 350 degrees until meringue starts to brown, about 5 minutes.