Pre-heat oven to 350 degrees. Lightly grease a 9 x 13 baking pan and line the pan with parchment paper. 1
Melt your butter in a small sauce pan over low heat.
Add in the remaining ingredients and stir until well-combined. Set aside.
Whisk together the flour, pumpkin pie spice*, baking soda, baking powder and salt.
In a separate bowl whisk together the wet ingredients: oil, brown sugar, eggs and vanilla using until no lumps remain.
Add in the sour cream and canned pumpkin and whisk until just combined.
Slowly add the flour mix into the wet ingredients with a rubber spatula and mix gently until just combined. Be careful not to over-mix.
Pour the batter into the pan and smooth out the top. Tap the pan on the counter top a few times to help ensure even consistency!
Crumble the streusel topping over the top until the entire cake batter is covered. You have plenty of streusel to cover the cake, so be generous!
Bake in the preheated oven for 40 minutes or until a toothpick comes out clean. Remove from the oven and let cool!
In a small bowl, use a metal whisk to combine all of the ingredients. Whisk vigorously until smooth.
Place the glaze in a small piping bag and snip a small hole in the corner. Drizzle over your cake and enjoy!