Prep the pan and oven: Heat oven to 350°F (175°C). Line a 9x13-inch pan with parchment, leaving overhang on the long sides for easy lifting.

Make the crust: In a bowl, whisk flour, sugar, and salt. Stir in melted butter and vanilla until the mixture looks like damp sand and clumps when pressed.

Press and par-bake: Firmly press the crust into the pan in an even layer. Prick a few times with a fork. Bake for 12–15 minutes until set and just starting to turn golden at the edges.

Mix the filling: In a separate bowl, whisk pumpkin, brown sugar, granulated sugar, eggs, evaporated milk, spices, salt, and vanilla until smooth and well combined. Do not overmix.

Pour and level: Pour the pumpkin filling over the hot crust. Tilt the pan gently to spread it into an even layer.

Bake: Return to the oven and bake for 30–35 minutes, until the center is set but still slightly jiggly, like custard. A toothpick should come out mostly clean near the center.

Cool completely: Place the pan on a rack and cool for at least 1 hour at room temperature, then chill for 2–3 hours to help it slice cleanly.

Slice and serve: Lift the bars out using the parchment. Cut into 16–24 squares. Serve plain or with a dollop of whipped cream and a light sprinkle of cinnamon.