Preheat the oven to 350 degrees F. Grease an 8×8 pan.
In a medium saucepan, boil maple syrup over medium heat for about 10 minutes. After about 10 minutes, measure it again in a glass measuring cup to make sure about 1/4 of it has evaporated. If it hasn’t, boil again for about 3 more minutes.
In a large mixing bowl or in a stand mixer bowl, mix melted butter, egg, vanilla, brown sugar, baking powder and salt.
Alternatively, mix in your flour and the heated maple syrup and mix until everything is combined. Pour into the prepared pan.
Bake for 30-35 minutes until golden brown and a toothpick stuck in the center comes out clean.