For the Cake:

1. Get your oven ready: Heat to 350°F and grease your 9×9 pan really well. I use butter because it never sticks, but cooking spray works too.
2. Mix dry stuff first: Whisk flour, baking powder, baking soda, salt, pumpkin pie spice, and cinnamon in a big bowl. Set it aside.
3. Wet ingredients time: In another bowl, whisk pumpkin, both sugars, sour cream, oil, eggs, and vanilla until smooth. Don’t worry if it looks weird at first – keep whisking.
4. Bring them together: Pour the flour mixture into the pumpkin mixture and stir just until combined. I always overmix and regret it – stop when you barely see flour streaks.
5. Bake it: Pour into your pan and bake 22-26 minutes. Stick a toothpick in the center – it should come out clean or with tiny crumbs. Cool completely before frosting (learned this lesson the hard way).

For the Espresso Buttercream:

1. Beat that butter: Use a mixer to beat butter until fluffy, about 3 minutes. It should look pale and doubled in size.
2. Add sugar gradually: Dump in powdered sugar bit by bit, beating after each addition. It’ll look dry and crumbly – that’s normal.
3. Coffee magic: Add milk, espresso powder, and vanilla. Beat on high for exactly one minute. This step makes it silky instead of grainy.
4. Fix the texture: Too thick? Add milk one teaspoon at a time. Too runny? More powdered sugar. You want it spreadable but not drippy.
5. Frost and cut: Spread evenly over cooled cake with a knife or offset spatula. Cut into squares and watch people fight over the corner pieces.