Lemon Sheet Cake

1 cup unsalted butter
1/2 cup water
1/2 cup lemon juice
2 cups granulated sugar
2 cups all-purpose flour
1/2 cup sour cream
2 eggs
2 teaspoons vanilla
1/2 teaspoon salt
1 teaspoon baking powder
1 tablespoon cornstarch

6 tablespoons unsalted butter
6 ounces softened cream cheese
4 cups powdered sugar
3 tablespoons lemon juice

How to make it

Preheat oven to 350 degrees F. Line a 9 x 13 pan with aluminum foil and lightly spray with nonstick cooking spray.
In a large saucepan, melt butter with water. Turn off heat and whisk in lemon juice, sugar, flour, sour cream, eggs, vanilla, salt, baking powder and cornstarch.
Pour into prepared pan. Bake 25-30 minutes or until toothpick inserted near the center comes out clean and cake springs back when lightly pressed.
While the cake is baking, make icing. In a medium saucepan, melt butter and cream cheese. Remove from heat and whisk in lemon juice and powdered sugar until smooth. Pour over warm cake.