Heat oven to 350°F. Line a 13 x 9-in. baking pan with foil, letting foil extend above pan at both ends. Coat foil with nonstick spray. Crust: Beat butter, flour and confectioners' sugar in a large bowl with mixer until blended (mixture will be crumbly). Press over bottom of pan. Bake 15 minutes, or until light golden. Leave oven on. Meanwhile, make Topping: In a large bowl, beat eggs, sugar, lemon zest and juice, flour and baking powder with mixer to combine. Add about 5 drops food color and beat until Topping is pink. Pour over the hot crust.