Mix the butter and brown sugar in a medium bowl with an electric mixer on high speed until combined.

Add the flour, pumpkin pie spice, and salt. Mix until the mixture resembles coarse crumbs.

Chill the streusel in the fridge while you prepare the coffee cake batter.

Preheat the oven to 350°F. Grease a 9x9-inch metal baking pan and line it with parchment paper.

In a medium bowl, whisk together the flour, pumpkin pie spice, baking soda, and salt. Set aside.

In a large bowl, cream the softened butter and granulated sugar with an electric mixer on high speed for 2 minutes.

Add the eggs and vanilla, mixing on medium speed until the mixture is pale and smooth, about 1 minute.

Mix in the buttermilk and canned pumpkin puree on medium-low speed until combined. The batter may look curdled, but it will smooth out when you add the dry ingredients.

Add the dry ingredients to the pumpkin mixture and mix on medium-low speed just until combined. Scrape the sides of the bowl as needed.

Pour the batter into the prepared baking pan and sprinkle the chilled streusel evenly over the top.

Bake for 60-70 minutes, or until a toothpick inserted into the center comes out clean with a few moist crumbs. If the top browns too quickly, cover it loosely with aluminum foil.

Let the cake cool in the pan on a wire rack.

While the cake cools, mix the cream cheese and maple syrup in a small bowl with an electric mixer on medium-high speed until smooth.

Gradually sift in the powdered sugar, mixing on low speed until fully combined. Then add the milk and mix until smooth.

Once the cake is cool enough to handle, lift it out of the pan using the parchment paper. Drizzle the cream cheese frosting over the top.