Preheat your oven to 350°F (175°C). Grease a 9×9 inch light metal baking pan, then line it with parchment paper to ensure easy removal of the cake after baking. Setting up the pan first helps streamline the process once your batter is ready.

In a medium bowl, whisk together the all-purpose flour, pumpkin pie spice blend, baking powder, baking soda, and salt, then set this mixture aside. In a large bowl, use an electric mixer to cream the softened butter and granulated sugar together on high speed for 2 minutes until light and fluffy. Next, add the eggs and vanilla extract, mixing on medium speed until the mixture is pale and smooth, about 1 minute. Add the buttermilk and canned pumpkin puree, mixing on medium-low speed until combined—the mixture may look curdled at this point, but that's expected. Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed just until the batter forms, scraping the bowl as needed. Pour the batter into your prepared baking pan, spreading it evenly.

Bake the cake in the preheated oven for 35-38 minutes, or until a toothpick comes out clean from the center. Allow the cake to cool in the pan on a wire rack for 30 minutes. Then use the parchment paper to lift the cake out and let it finish cooling completely on the rack. It's important to let the cake cool fully so it doesn't fall apart or melt the soak and frosting later.

While the cake is cooling, combine the strong brewed espresso or coffee, whole milk, sweetened condensed milk, pumpkin pie spice, and vanilla extract in a measuring cup or container with a spout. Stir until everything is completely mixed. I find this soak adds a rich and festive flavor that really sets this cake apart.

In a large bowl, beat the softened unsalted butter on high speed with an electric mixer until pale and fluffy, about 5-10 minutes. Add the cold cream cheese and mix on medium speed until the mixture is smooth and fluffy. Gradually sift in powdered sugar, mixing on low speed at first and then on high speed for 1 minute until the frosting is fluffy. Dissolve the instant espresso powder into vanilla extract in a small ramekin, then add this mixture along with pumpkin pie spice to the frosting. Beat on medium-low to combine, then on high until light and airy. For a creamier frosting, I always make sure the cream cheese is chilled before adding it, which helps the frosting hold its shape better.

Once the cake is completely cooled, use a sharp knife to trim a very thin layer from the top—this helps the latte soak absorb better. Carefully transfer the cake to a serving plate. Using a wooden stick or the handle of a spoon, poke holes all over the top of the cake. Slowly pour the latte soak mixture (from Step 4) over the cake, allowing it to seep into the holes. Spread a thick, even layer of espresso cream cheese frosting (from Step 5) over the cake with an offset spatula. Finish by sprinkling extra pumpkin pie spice over the frosting. For extra flair, I like to dust a bit more pumpkin pie spice on top just before serving.