Preheat oven to 350.
Line a baking pan with parchment paper, set aside.
Trim a very thin slice from the round side of each peach half (so the halves will stand flat on the baking pan). Dip peach halves in melted butter to coat.
Arrange peach halves, cut side up, in prepared pan. Sprinkle cut side of peaches with cinnamon sugar; set aside.
In medium mixing bowl, beat cream cheese with a mixer on medium speed until smooth. Add sugar, egg yolk and vanilla. Beat until combined. Spoon cream cheese mixture into peach centers.
Bake, uncovered, about 30 minutes or until lightly browned and softened. Serve warm or at room temperature.