Preheat your oven to 350°F (175°C) and grease an 8x8-inch baking pan or line it with parchment paper.
In a large mixing bowl, combine the mashed sweet potatoes and melted butter, stirring until well mixed.
Add the brown sugar and granulated sugar, and mix until smooth.
Beat in the eggs one at a time, followed by the vanilla extract.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in the salted caramel sauce and chopped nuts if using.
Pour the batter into the prepared baking pan and spread it evenly.
Drizzle a little extra caramel sauce on top and sprinkle with flaky sea salt.
Bake for 25-30 minutes or until a toothpick inserted into the center comes out clean.
Allow the blondies to cool in the pan for about 10 minutes before transferring to a wire rack to cool completely.
Cut into squares and serve. For best flavor, let them sit for a few hours or overnight to allow the flavors to meld.
