Preheat oven to 350°F. Line a 24-cup mini muffin tin with parchment paper liners.
Combine flour, pumpkin spice, baking soda, and salt in medium bowl. Mix and set aside.
Combine pumpkin puree, sugar, egg, oil, and juice in a large mixing bowl. Whisk until just blended.
Add flour mixture to pumpkin mixture and stir with a fork or whisk until just moistened.
Spoon batter into prepared muffin cups using a Tablespoon until 3/4 filled. Approx. 1 heaping TBSP per cupcake.
Bake in preheated oven for 16-19 minutes, checking for doneness with a toothpick inserted to the center of the cupcake. Mine are usually perfect at 17-18 minutes (I'm at sea level) but oven times may vary.
Carefully remove cupcakes from muffin tin and allow to cool completely on a wire baking rack.
While they cool, make the frosting.
To make the cinnamon cream cheese butterream, combine softened butter and cream cheese in a medium/large mixing bowl. Use an electric hand-mixer and beat until lusciously creamy and free of lumps.
Beat in vanilla and salt until incorporated. Adjust mixer speed to low and, in batches, gradually add powdered sugar while mixing the frosting, followed by cinnamon. Start with 1/2 tsp and increase to taste. The taste-testing part is my favorite! After the powdered sugar and cinnamon is incorporated, beat at medium speed for a few more seconds to fluff, then add to a piping bag to frost cooled cupcakes.
After frosting, feel free to sprinkle cupcakes with a teeny bit of extra ground cinnamon or even pumpkin pie spice or sprinkles as a tasty garnish.
Nutrition Facts below are estimated using an online recipe nutrition calculator. Adjust as needed and enjoy!