1. To prepare filling, combine sugar and cornstarch in a small saucepan. Stir in 1/3 cup water, orange juice, lemon juice, rind, and yolk. Bring to a boil; reduce heat and cook, stirring constantly, about 3 minutes or until very thick. Transfer to a bowl, and chill. (To chill quickly, place the bowl in the freezer and stir every couple of minutes until room temperature.)
2. To prepare cupcakes, preheat oven to 350°. Coat 36 miniature muffin cups with cooking spray.
3. Combine flour, sugar, baking powder, baking soda, and salt in a medium bowl. Add coconut milk, eggs, oil, and vanilla; beat with a mixer at low speed until smooth.
4. Spoon 2 teaspoons batter into each muffin cup. Add 1 teaspoon filling to center of each cup. Top with 1/2 teaspoon batter; spread over filling.
5. Bake at 350° for 15 minutes or until muffins spring back when touched lightly in center. Cool 5 minutes in pan; remove muffins from pan. Let cool completely before frosting.
6. To prepare frosting, beat butter and Neufchâtel cheese with a mixer at high speed until smooth. Add the sugar; beat well. Add rind and coconut milk; beat until smooth.
7. Generously frost tops of cupcakes; sprinkle with coconut.