Preheat the oven to 350°F (175°C) and grease a 10x15-inch rimmed baking sheet (jelly roll pan). Make sure the pan is well coated so the bars release cleanly.

Whisk together all-purpose flour, baking powder, baking soda, fine sea salt, ground cinnamon, ground ginger, ground nutmeg, and ground cloves in a medium bowl. Mix until the spices are evenly distributed.

In a large bowl, beat the eggs and granulated sugar with a mixer on medium speed for 1–2 minutes until pale and slightly thickened. The mixture should look lighter and feel a bit thicker.

Beat in the vegetable oil, pumpkin purée, and pure vanilla extract until smooth. Stop and scrape the bowl if streaks remain.

Add the dry ingredients and mix on low speed just until no streaks of flour remain. Mix only until combined to keep the crumb tender.

Pour the batter into the prepared pan and spread it evenly to the edges. Use gentle smoothing so the thickness is consistent.

Bake for 25–30 minutes, until the top springs back when lightly pressed and a toothpick in the center comes out clean. Look for a set center and a lightly browned top.

Cool completely in the pan on a wire rack, about 1 ½ hours. The bars must be fully cool before frosting to prevent melting.

Beat the cream cheese and unsalted butter on medium speed for 2 minutes until smooth and creamy. The mixture should be free of lumps.

Add the powdered sugar and fine sea salt, then beat on low until combined. Stop once no dry pockets remain to avoid a sugar cloud.

Beat on medium until light and fluffy. The frosting should look airy and hold soft shape.

Beat in the milk and vanilla on medium until the frosting is silky and spreadable. Adjust texture with a tiny splash more milk if needed.

Spread the frosting evenly over the cooled pumpkin bars with an offset spatula. Cover to the edges for a uniform layer.

Dust lightly with ground cinnamon, slice into 24 bars, and serve. Cut with a clean motion for neat edges.