Preheat your oven to 350°F (175°C) and prepare an 8-inch square baking pan with nonstick spray or parchment paper.

In a small bowl, combine light brown sugar, flour, chopped walnuts, cinnamon, and melted butter to create a streusel topping.

In a large bowl, whisk together flour, baking powder, baking soda, and salt until well combined.

In another bowl, whisk together brown sugar, maple syrup, vegetable oil, milk, eggs, and optional maple extract until smooth.

Gently combine the wet and dry mixtures, stirring until just combined; avoid overmixing.

Spoon half of the batter into the prepared pan, add half of the streusel topping, then spread remaining batter and top with the rest of the streusel.

Bake for about 35 minutes, or until golden brown and a toothpick comes out clean.

Allow the cake to cool for 15 minutes before mixing together powdered sugar and maple syrup for icing to drizzle over the cake.