To make the filling, combine pears, cranberries and maple syrup in a small saucepan, set over medium-high heat and bring to a simmer.

Reduce heat to medium-low and cook, stirring occasionally, for 30 minutes or until pears are very tender. Remove from heat and stir in orange zest.

Let cool, then reserve 1/4 cup of the filling to use for making the topping.

Transfer 1 cup of the remaining filling to a food processor or blender and blend until it forms a jam-like consistency. Add blended filling to remaining filling and stir to combine.

To make the topping, combine oats, pistachios and reserved 1/4 cup filling in a small bowl.

To make the crust, preheat the oven to 325°F. Butter and flour a 9-inch square baking dish.

Place pistachios in a food processor and pulse until finely ground, being careful not to create a paste.

Transfer to a large bowl and add oats, brown sugar, brown rice flour, potato starch, tapioca starch, baking powder, xanthan gum, salt and cardamom. Stir until well combined.

Using a pastry blender or 2 butter knives, cut butter into oat mixture until coarse crumbs form.

Add egg and stir to form a dough. Press dough evenly into the bottom of the prepared pan.

Spread filling over dough, then sprinkle topping evenly over filling, pressing lightly so it adheres.

Bake until golden brown, about 45 minutes. Transfer the pan to a wire rack and let cool completely, then cut into 16 squares.