• Preheat your oven to 350F and line an 8*8 inch baking pan with parchment paper. You can also lightly grease the sides of the pan with coconut oil or vegan butter.

Make the streusel:

• Add the flour, brown sugar, and pumpkin pie spice to a small bowl and whisk together. Then, add the room-temperature vegan butter and cut it into the dry ingredients until you have a crumbly mixture that holds together. You can also pulse everything together in a food processor.
• Set aside the streusel for later.

Make the pumpkin cake:

• Add the oat milk and apple cider vinegar to a large mixing bowl. Whisk together and let sit for about 2 minutes until the milk curdles to create a vegan buttermilk.
• Then, mix in the remaining wet ingredients, including the pumpkin puree, brown sugar, white sugar, melted vegan butter, and vanilla bean paste.
• Add the dry ingredients to the bowl, starting with the all-purpose flour and pouring the pumpkin pie spice, baking powder, baking soda, and salt on top.
• Gently whisk into the wet ingredients until you have a thick batter. I recommend using a spatula so the batter does not get over-mixed.

Layer & bake:

• Add the pumpkin cake batter to the parchment-lined pan and use a spatula to spread it out evenly.
• Then, sprinkle the streusel on top.
• Add the pumpkin coffee cake to the oven and bake for about 40 minutes, until cooked through.
• Let the cake cool in the pan for about 10 minutes, then remove it and transfer to a wire rack to finish cooling.

Add icing & serve!

• Once the cake has cooled, make the icing. Whisk together the powdered sugar, pumpkin pie spice, and oat milk until you have a smooth icing.
• Then, drizzle the icing over the coffee cake.
• Slice the cake into 9 large squares, serve, & enjoy!