Yes, this cake is homage to everyone’s favorite Starbuck’s Pumpkin Spice Latte beverage. By the way, turns out their drink contains no pumpkin! It’s the spices that make you think you are experiencing “pumpkin”, since we are so used to tasting them in pumpkin pies and pumpkin bread. This easy coffee cake is packed with pumpkin and pumpkin pie spice as well as a bit of coffee so it’s the real deal. It stays super moist from the yogurt, making it a great fall bake sale item or to have on hand during the winter holidays for entertaining. The buttery crumb topping adds texture and flavor. By the way, pumpkin pie spice is a combination of spices, usually cinnamon, ginger and then the addition of some or all of cloves, nutmeg and/or allspice. The problem is that there is no standard blend so you have to try different ones to see which you like. And don’t be confused about “allspice”. It is not a blend of spices itself but rather its own spice that looks somewhat like large peppercorns in its whole form. I like both McCormick Pumpkin Pie Spice (cinnamon, ginger, nutmeg and allspice) and Frontier Pumpkin Pie Spice blends (cinnamon, ginger, cloves and nutmeg. — Dédé Wilson, founder of Bakepedia
Melt the butter in a medium mixing bowl in microwave. Whisk in the brown sugar, granulated sugar, pumpkin pie spice, cinnamon, and salt, and then stir in flour. Create crumbs by squeezing together the mixture with fingers. (You can melt the butter on stovetop too, if you like, then transfer to a mixing bowl). Set aside.
Position a rack in center of oven. Preheat the oven to 325 degrees F. Coat an 8-inch square baking pan with nonstick spray.
Whisk together the flour, baking powder, baking soda, pumpkin pie spice, and salt in a medium bowl to aerate and combine; set aside.
In a stand mixer fitted with a paddle attachment on medium-high speed, beat the butter until creamy, about 2 minutes. Add the brown sugar gradually and continue to beat for, about 3 minutes at medium-high speed, until very light and fluffy. Beat in the pumpkin purée. Dissolve the instant espresso in the vanilla extract then beat that in. Add the eggs one at a time, beating well after each addition, scraping down the bowl as needed. The mixture might look curdled; that’s okay. Add the flour mixture in three additions, alternating additions with the yogurt. Begin and end with the flour mixture and beat briefly until smooth.
Scrape the batter into the prepared pan and smooth the top with a small offset spatula. Sprinkle the crumb topping evenly over the batter.
Bake for until a bamboo skewer inserted in the cake shows a few moist crumbs, 55 to 60 minutes. The crumb topping will be golden brown and perhaps a bit crusty on top. Cool in the pan on a rack for at least 20 minutes. The cake is ready to serve warm or at room temperature; simply cut into squares. Store at room temperature in an airtight container for up to 3 days.