Gather cake ingredients and frosting ingredients.
Preheat the oven to 350 degrees F (175 degrees C).
To make the cake: Beat pumpkin puree, sugar, oil, and eggs with an electric mixer in a medium bowl until well combined.
Sift together flour, cinnamon, baking powder, baking soda, and salt in a separate bowl.
Stir into pumpkin mixture until thoroughly combined.
Spread batter evenly into an ungreased 10x15-inch jelly roll pan.
Bake in the preheated oven until cake bounces back when gently pressed, 25 to 30 minutes. Remove from the oven and let cool.
While the cake is cooling, make frosting: Beat together butter and cream cheese until smooth; stir in vanilla. Add confectioners' sugar a little at a time, beating until mixture is smooth.
Spread frosting evenly on top of cooled cake. Cut into 24 squares.
