Line an 8x8x2-inch pan with parchment paper, allowing two sides to hang over, making it easier to remove bars once cooled.
SHORTBREAD: In a large bowl, whisk together the melted butter, sugar, salt and orange zest. Add egg yolk, continue to whisk until combined. Stir in flour with a heavy spoon or your hands. Pour dough into prepared pan and press down evenly with your hands until the pan is covered. Refrigerate for 30 minutes to one hour. Remove and bake at 350 degrees for 25-28 minutes, until lightly browned. Allow to cool while you are preparing the caramel.
CARAMEL TOPPING: In a heavy bottomed pot, combine the butter, brown sugar, sugar corn syrup, sea salt, and heavy cream. Bring to a boil and stir until sugars are dissolved and the mixture is well combined. Using a candy thermometer, heat caramel to 230 degrees. Remove from heat and stir in vanilla and orange extracts. Allow to cool for a couple of minutes, then pour over the shortbread base. Sprinkle with sea salt, then refrigerate for several hours. Once chilled, cut into small squares, serve and enjoy!