Prepare Oven and Dish: Preheat your oven to 375∘F (190∘C). Lightly grease the bottom and sides of the ceramic baking dish.
Toast Walnuts: Spread the chopped walnuts in a single layer on a small, dry skillet over medium heat. Toast for 3-5 minutes, stirring frequently, until they become fragrant and lightly browned. Immediately remove from the skillet and set aside to cool.
Core the Pears: Wash and dry the pears. Slice each one in half lengthwise. Use a melon baller or a small spoon to carefully scoop out the core and seeds from each half. To help them sit securely, shave a tiny slice off the rounded bottom of each pear half so they rest flat.
Mix the Glaze: In a small mixing bowl, whisk together the melted butter, pure maple syrup, vanilla extract, pumpkin pie spice, and fine sea salt until fully combined.
First Bake: Arrange the pear halves in the prepared baking dish with the cored side facing up. Drizzle approximately half of the maple glaze evenly over the pears, allowing it to pool in the cored centers. Bake for 25 minutes.
Final Bake: Carefully remove the dish from the oven. Spoon the remaining glaze over the pears and sprinkle with the toasted walnuts. Return the dish to the oven and bake for an additional 10-12 minutes, or until the pears are fork-tender and the glaze is bubbling at the edges. Let cool for a few minutes before serving.