In a small bowl, soak poppy seeds in milk for 2 hours.
Preheat oven to 325 degrees F. Generously grease and flour a 12-cup bundt pan.
In a large bowl, combine flour, baking powder, and salt; set aside.
In a large bowl, cream butter until smooth, gradually stir in sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Beat in orange zest, vanilla extract, and poppy seed mixture. Stir in flour mixture and orange juice alternately in three additions, beginning and ending with flour. Pour batter into prepared pan.
Bake 50 to 60 minutes or until a toothpick inserted in center comes out clean. Cake is done when the internal temperature registers approximately 205 to 209 degrees F. on your cooking thermometer.
Remove from oven and cool 15 minutes on a wire rack; remove from pan and invert onto a cake plate. Spoon Orange Glaze over warm cake.
Makes 16 servings.
1 cup powdered (confectioner's) sugar
1 teaspoon grated orange zest
2 to 3 tablespoons fresh-squeezed orange juice
In a small bowl, combine sugar and orange zest. Stir in orange juice until smooth.