Pour evaporated milk into an 8x8x2-inch baking pan. Freeze milk for 20 to 30 minutes or until soft crystals form throughout milk. Pour milk into a chilled mixing bowl. Beat with an electric mixer on high speed for 2 to 3 minutes or until soft peaks form (tips curl).
Add lemon juice and vanilla; whip to mix well. Fold in powdered sugar. Serve immediately. Makes 2-1/2 cups.