Heat the oven to 350°F. Line a large baking sheet with parchment paper and grease the edges. Set aside.
In a bowl, combine flour, cinnamon, pumpkin pie spice, baking soda, and salt. Whisk until evenly blended.
In a large bowl, beat the eggs with the pumpkin puree, sugars, oil, and vanilla until smooth and glossy.
Gradually add the dry ingredients into the pumpkin mixture in thirds, folding gently until just mixed. Avoid over-mixing.
Spread the batter evenly in the prepared pan. Bake 18–22 minutes, or until a toothpick comes out clean. Let cool on a rack briefly, then chill in the freezer 15–20 minutes — this makes cutting cleaner.
Beat the softened butter on medium speed until light and creamy. Add powdered sugar gradually. Scrape down the bowl, then pour in the heavy cream and caramel. Beat until smooth and fluffy. Add the pinch of salt to balance sweetness.
Use a ~2-inch round cutter (or small glass) to cut circles from the cooled pumpkin sheet. Each cake will have two layers.
Pipe or spread a generous layer of caramel buttercream on one cake circle, stack another on top, then top with more frosting. Drizzle extra caramel or sprinkle spices if desired.
Serve at room temperature for the best texture. Store leftover frosted mini cakes in the fridge and let soften slightly before eating.
