Preheat the oven to 350ºF and line an 8 X 8 inch pan with parchment paper. In the bowl of a stand mixer fit with a paddle attachment, or in a large mixing bowl with a wooden spoon, beat together the cooled butter, maple syrup, eggs, brown sugar, and vanilla until a smooth batter forms.

In a separate mixing bowl, whisk together the flour, baking powder, baking soda, and salt. With the mixer on low speed, or using a wooden spoon, gradually add the dry ingredients to the butter mixture, beating until well-combined. Turn off the mixer and use a spatula to fold the chopped pecans into the batter, reserving 1/4 cup of pecans for topping.

Pour the batter into the prepared pan, smoothing the top with a spatula. Bake in the preheated oven for 30 to 35 minutes, or until the edges begin to brown and a toothpick inserted in the center comes out clean. Remove the cake from the oven and allow to cool 10 minutes in the pan before lifting the cake out with the parchment paper and allowing it to cool completely on a cooling rack.

In a small bowl, whisk together the powdered sugar, maple syrup and vanilla extract for the glaze. Whisk until smooth and just thin enough to drizzle slowly from the end of a spoon. If the glaze seems to thick, add a few more drops of maple syrup and whisk to combine. If the glaze seems to thin and watery, add more powdered sugar, a teaspoon at a time, and whisk to combine. Once glaze is the right consistency, use a spoon to drizzle the glaze over the top of the cooled cake. Sprinkle the reserved chopped pecans over the glaze. Cut cake into squares and serve.