Preheat the oven to 350°F (175°C). Grease and line a 9x13 inch baking pan with parchment paper.

In a mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.

In another bowl, whisk together the flour, baking powder, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Spread the batter evenly in the prepared baking pan.

Bake for 25-30 minutes or until a toothpick inserted in the center comes out clean.

Let the bars cool in the pan on a wire rack.

In a saucepan over medium heat, melt the granulated sugar, stirring constantly until it turns a deep amber color.

Carefully add the butter and stir until melted and combined.

Slowly pour in the heavy cream while stirring, being cautious of splattering.

Remove from heat and stir in the sea salt. Let cool slightly.

Pour the salted caramel over the cooled butter bars and spread evenly.

Allow the caramel to set before cutting into squares.