Preheat oven to 350 degrees.

In a bowl, make the streusel topping. Combine the flour, brown sugar, cinnamon, nutmeg and melted butter. Use a fork to mix together. Consistency should be crumbly and gravel-like.

In a mixing bowl, mix together the donut batter. Combine the spice cake mix, pumpkin, eggs and 3 Tbsp. of melted butter. Use a hand mixer, stand mixer or manually whisk with a whisk. Batter will be very thick. Transfer the batter to a resealable gallon-sized plastic bag. Cut off one of the corners to create a 3/4" opening. Set bag aside.

Begin piping the pumpkin donut batter into the donut cavities of the donut pan. Top the batter of each donut with 1-2 Tbsp. of streusel topping.

Bake the donuts at 350 degrees for 9-10 minutes. Once done baking, let the donuts cool in the pan for about 5 minutes before transferring to a wire cooling rack. Repeat the process until all batter is baked into donuts.

Once donuts are baked and on cooling rack. Mix together the glaze. In a bowl, combine the powdered sugar, milk and vanilla. Mixture should be thick enough to coat the back of a spoon. Drizzle the glaze over the donuts. Enjoy right away. Let the glaze dry to room temperature before storing the donuts.