Preheat the oven to 350°F. Grease and lightly flour a 9 inch square baking pan. Set aside.
Make the crumb topping first. In a small bowl, toss brown sugar, flour, pecans, spice, and salt together. Cut in the cold butter using a pastry blender or a fork. Mix to create clumps and crumbs. Set aside.
To make the cake, combine flour, brown sugar, baking soda, baking powder, salt, and pumpkin pie spice in the bowl of your stand mixer. With the paddle attachment on and speed on low, slowly add pieces of the butter until you've added the entire cube. Increase speed taking care to not make a huge mess, and mix until your dry mixture is well coated in the butter.
In a separate bowl, whisk the pumpkin, maple syrup, buttermilk and egg together until combined. With the mixer running on low, pour half of the wet ingredients into the dry ingredients. Increase speed to medium and mix well until light and fluffy, about a minute. Add remaining liquid mixture and mix just until combined. Batter will be very thick. Add to prepared baking dish. Spread to make an even surface.
Pour half of the crumb topping evenly on top and gently swirl to incorporate some of it into the batter. Then add the remaining struesel topping and press down into the batter.
Bake the cake for 30-40 minutes. Check the cake's doneness by inserting a toothpick into the center. If the toothpick comes on clean with a moist crumb or two, the cake is done. If the toothpick has wet batter on it, bake the cake for 5 more minutes.
Store cake in air tight container. I kept it in a gallon sized freezer bag with all the air squeezed out and it was even better the next day!