Preheat the oven to 350°F (175°C). Grease a 9-inch (23 cm) round cake pan with butter or cooking spray.
In a large mixing bowl, cream the butter and sugar together until light and fluffy, using an electric mixer.
Beat in the eggs one at a time, scraping down the sides of the bowl as needed.
In a separate bowl, whisk together the flour, baking powder, and salt.
Gradually add the dry ingredients to the butter mixture, mixing until just combined.
Stir in the almond extract.
Press the dough into the prepared cake pan using your hands or a spatula, making sure the dough is evenly distributed.
Use a knife to score a criss-cross pattern on the top of the dough, then sprinkle the sliced almonds on top (if using).
Bake for 25-30 minutes, or until the edges are golden brown and the center is set.
Let the boterkoek cool for a few minutes in the pan, then transfer it to a wire rack to cool completely.
Cut the boterkoek into 8 wedges and serve.
Notes
Tips and Tricks
Make sure the butter is at room temperature before you start mixing the dough. This will ensure that the boterkoek has a smooth and even texture.Use a knife to score a criss-cross pattern on the top of the dough before baking. This will make it easier to cut the boterkoek into wedges after it's baked.Don't overmix the dough after you add the dry ingredients. Overmixing can result in tough boterkoek.If the dough is too sticky to press into the pan, you can refrigerate it for 10-15 minutes to firm it up.