Preheat your oven to 350 °F (175 °C). Grease a 9-inch tart pan with removable bottom.
In a medium bowl, combine the walnut meal, flour (or almond flour), melted butter, brown sugar, vanilla extract and sea salt. Stir until the mixture comes together and feels like damp sand.
Press the crust mixture evenly into the bottom and ¼ up the sides of the tart pan. Use the back of a spoon to smooth the surface. Bake for 10–12 minutes, until set and just beginning to colour at the edges. Remove and let cool slightly.
Meanwhile, in a small bowl whisk together the caramel syrup, melted butter, cinnamon, nutmeg, allspice and lemon juice.
Arrange the sliced pears in a concentric fan pattern over the crust (or any aesthetic layout you like). Pour the glaze evenly over the pears, gently brushing so all the slices are coated and the walnuts will catch some of the glaze. Sprinkle the toasted walnuts over the top.
Bake the tart on a sheet pan (to catch any drips) for 18-20 minutes, or until the pear slices are tender and the glaze is bubbling lightly around the edges. The crust edges should be golden but not burnt.
Remove from oven and let rest 10 minutes so the glaze settles. Slice and serve warm or at room temperature with a dollop of whipped cream or vanilla ice cream if desired.
