Now, here’s how to make your amazing Pumpkin Coffee Cake step-by-step:

1. Preheat Your Oven: Start by preheating your oven to 350°F (175°C). Grease and flour a 9×13-inch baking dish.

2. Mix Dry Ingredients: In a large bowl, whisk together the flour, granulated sugar, brown sugar, baking powder, baking soda, cinnamon, nutmeg, allspice, and salt until well combined.

3. Combine Wet Ingredients: In another bowl, combine the pumpkin puree, vegetable oil, eggs, and vanilla extract. Mix until smooth.

4. Combine Mixtures: Gradually add the wet ingredients to the dry ingredients, stirring gently until just combined. Be careful not to over-mix.

5. Prepare Topping: In a small bowl, mix together the chopped nuts, rolled oats, and cold butter. Use a fork or pastry cutter to combine until crumbly.

6. Pour Batter: Pour the cake batter into the prepared baking dish, spreading it evenly.

7. Add Topping: Sprinkle the crumb topping generously over the cake batter.

8. Bake: Place the baking dish in the preheated oven and bake for 40-45 minutes, or until a toothpick inserted in the center comes out clean.

9. Cool the Cake: Remove the cake from the oven and let it cool in the dish for about 15-20 minutes before transferring it to a wire rack to cool completely.

10. Optional Glaze: If desired, mix powdered sugar with a little water or milk to create a glaze. Drizzle it over the cooled cake for an extra touch of sweetness.