Preheat oven to 350°F. Grease or line an 8x8 pan.
Mix streusel flour, brown sugar, cinnamon + salt. Cut in cold butter until crumbly; refrigerate.
Whisk cake flour, baking powder, baking soda, salt + pumpkin pie spice.
Beat softened butter + sugars until fluffy. Mix in applesauce, pumpkin, Greek yogurt + vanilla.
Add dry ingredients and mix just until combined.
Spread batter into pan and top evenly with streusel. Bake 35–45 min, until a toothpick comes out clean.
Cool 15–20 min. Mix glaze ingredients, adding milk as needed, then drizzle over cake.
