How to Make It
Place a rack in the lower third of the oven and heat to 350° F. Butter a 9- by 13-inch cake pan and line with parchment, leaving an overhang on two sides; butter the parchment.
Pulse the flour, sugar, baking powder, salt, and ¼ cup pine nuts in a food processor until the pine nuts are finely ground. Add 8 tablespoons butter and pulse until coarse crumbs form. Add the egg and pulse until evenly incorporated and large clumps form. Press the dough evenly into the bottom of the prepared pan, creating a little lip along the edges. Freeze until firm, about 10 minutes.
Spread the marmalade in an even layer over the chilled dough. Sprinkle the remaining ½ cup pine nuts on top.
Bake until the dough is cooked through and the marmalade is bubbling, about 45 minutes. Cool completely in the pan on a rack. Holding the paper overhang, lift the layers out of the pan and transfer to a cutting board. Trim the edges, then cut the rectangle into 2-inch squares.
Storage tip: The bars can be stored in an airtight container for up to 3 days.