Combine sugar and juice in a small, heavy saucepan. Place over medium-low heat; cook 5 minutes or until sugar dissolves. (Do not stir.) Cover, increase heat to medium, and boil 30 seconds (this will dissolve any sugar crystals clinging to the sides of the pan). Uncover and boil 2 minutes or until amber or golden. (Do not stir.)
Remove from heat; let stand 1 minute. Carefully add butter, stirring until butter melts. Gradually add milk, stirring constantly (caramel will harden and stick to spoon). Place pan over medium heat; cook 2 minutes or until caramel melts and mixture is smooth, stirring constantly. Remove from heat; stir in liqueur, vanilla, and salt. Pour caramel sauce over oranges; sprinkle with pecans.