Place an oven rack in the center position and preheat the oven to 350 degrees F. Grease an 8x8 pan using baking spray.

Prepare the frangipane: In a medium-sized bowl, use an electric mixer to cream together the butter and sugar until smooth. Add the egg and almond extract, then add the almond and all-purpose flour, mixing until smooth and using a spatula to scrap the sides as needed. Set aside

In a large bowl, whisk together the melted butter and brown sugar until smooth, then whisk in the egg, vanilla extract, and almond extract until smooth. In a separate bowl, whisk together the flour, baking soda, baking powder, and salt. Use a spatula to stir the dry ingredients into the wet until smooth, scraping the sides and bottom of the bowl as needed.

Transfer the batter to the greased pan, spreading it evenly. The batter will be sticky, so take your time smoothing it into the sides and corners. Spread the frangipane evenly on top, then top with the sliced almonds.

Bake for 30-35 minutes, until the top is golden brown and a toothpick comes out clean.

Let the blondies cool, then dust with as much confectioners' sugar as you like. Cut into 9 or 16 blondies and serve.