How to Make It
Prepare the Blueberry Bread Pudding: Preheat oven to 400°F. Spread cake cubes in a single layer in a lightly greased (with cooking spray) large rimmed baking pan. Bake in preheated oven until lightly toasted, 10 to 12 minutes. Transfer to a wire rack, and cool 15 minutes. Reduce oven temperature to 350°F.
Whisk together eggs, sugar, lemon zest, vanilla, and salt in a large bowl until well blended. Whisk in milk and heavy cream until well blended.
Add cake cubes to egg mixture, and gently toss until coated. Let stand 20 minutes. Stir in 1 cup of the blueberries.
Spread pound cake mixture in a lightly greased (with cooking spray) 11- x 7-inch baking dish; sprinkle top with remaining 1 cup blueberries. Bake at 350°F until set in the center, 45 to 50 minutes.
Prepare the Lemon Hard Sauce: Beat together softened butter, lemon zest, and lemon juice at medium speed with an electric mixer until creamy. Gradually add powdered sugar, beating until light and fluffy. Serve immediately with warm bread pudding.