Preheat oven to 350°F. Line a 9-inch square baking dish with parchment paper.

In a small bowl, mix diced apples with a teaspoon of flour and set aside.

In a large bowl, combine melted butter and brown sugar. Mix until smooth.

Add egg and vanilla extract to the sugar mixture and beat well.

Stir in flour and salt until just combined. Fold in diced apples and toffee bits.

Pour batter into prepared pan and bake for 25 minutes or until a toothpick inserted in the center comes out clean.

Allow to cool completely before frosting.

Prepare frosting by beating softened butter until fluffy, then gradually add powdered sugar, caramel sauce, and heavy cream. Mix until smooth and creamy.

Spread frosting over cooled blondies. Sprinkle additional toffee bits on top if desired.