Preheat oven to 350℉.
To make the crust, beat butter and brown sugar in a mixer until smooth, and light in color, about 5 minutes.
Add flour and sea salt and mix until just incorporated and crumbly. Dough should press and hold together like wet sand.
Press into a 9x13 baking dish lined with parchment paper or foil, and bake until golden brown, about 30 minutes.
While crust is baking, mix up filling. In a large bowl, whisk together eggs, granulated sugar, and brown sugar.
Add pumpkin, maple syrup, corn syrup, sea salt, and pumpkin spice. Stir to combine.
Stir in pecans.
Pour over warm crust, and bake until set, about 45 minutes longer.
Cool to room temperature, then turn upside down onto a cutting board to remove parchment/foil and cut into squares/bars.