Line an 8 or 9 inch square baking pan with two long strips of parchment paper arranged in a cross so the ends hang over the edges, creating easy handles for lifting the finished bars.

In a large bowl, combine the graham cracker crumbs, brown sugar, sea salt, and pumpkin pie spice. Pour in the melted butter and stir until every crumb is moistened.

Press the crust mixture firmly and evenly into the bottom of the prepared pan using a flat bottomed measuring cup or glass. Set aside while you make the filling.

In a chilled bowl, whip the heavy cream until stiff peaks form. Cover and keep chilled in the refrigerator while making the filling.

In a separate large bowl, beat the softened cream cheese, granulated sugar, and salt until completely smooth. Add the vanilla, Meyer lemon juice, pumpkin puree, and pumpkin pie spice, then beat again until silky and well blended.

Using a rubber spatula, gently fold the whipped cream into the pumpkin mixture just until no streaks remain and the batter looks light and fluffy.

Scrape the filling over the prepared crust and smooth the top with an offset spatula. Refrigerate for at least 8 hours or overnight. For cleaner slices, freeze for 1 hour before cutting.

Use the parchment handles to lift the chilled cheesecake onto a cutting board. Trim the uneven edges, then slice into 12 bars in a 4 by 3 grid, wiping the knife clean after each cut.

Whip the cream, powdered sugar, and vanilla until stiff peaks hold. Transfer to a piping bag fitted with a large star tip, pipe a swirl on top of each bar, and sprinkle lightly with pumpkin pie spice before serving.