How to Make It
Stir together sugar and cornstarch in medium saucepan; gradually stir in 1-1/4 cups pineapple juice. Cook over medium heat, stirring occasionally 5 to 6 minutes or until mixture boils and thickens.
Remove from heat and stir in butter, pour into bowl. Place plastic wrap directly on filling chill 2 to 8 hours.
Place baking cups in 2 (12-cup) muffin pans and lightly coat with cooking spray.
Beat eggs with cinnamon at medium speed with electric mixer 2 minutes. Add sour cream, and pineapple juice, beating well. Add cake mix, and beat at low speed until just blended, about 2 minutes. Spoon batter into prepared cups, filling 2/3 full.
Bake at 325°F., 25 to 27 minutes or until wooden pick inserted in center comes out clean. Remove from pans to wire rack to cool completely.
Scoop out centers of cupcakes, using a 1-inch melon baller and leaving a 1/2-inch border around edges. Discard or reserve centers for another use. Spoon a heaping tablespoonful Pineapple Filling into center of each cupcake.
Pipe cupcakes with butter cream frosting.