Preheat oven to 375 degrees. Set aside an 8x8 square baking dish or a medium size gratin dish.
In a large mixing bowl, toss the pears in the lemon juice. In a small mixing bowl whisk together the sugar, cornstarch, cinnamon and cardamom. Sprinkle over the pears and toss to coat, pour into the baking dish.
In a medium size mixing bowl whisk together the flour, oats, brown sugar, salt, baking soda, baking powder and cinnamon; set aside.
In a small saucepan set over medium heat, add the 4 tablespoons of butter. Heat until the butter foams then begins to brown and become speckled (about 3-5 minutes), whisking every so often. Pour into the bowl with the topping ingredients and mix until crumbles form. Sprinkle over the filling.
Place in the oven and bake for 35-45 minutes or until pears are tender and topping is golden brown. Remove from the oven and allow to cool 20 minutes, serve warm.
Notes
*You can also use melted butter instead of browned butter. -You can toss in 2/3 c. of fresh cranberries to the filling, just increase the granulated sugar to 1/3 c. -You can add 1/4 c. of your favorite finely chopped nuts to the topping.