Preheat the oven to 350 °F. Grease a 9-inch cast iron skillet or baking dish with butter.
Pear Crisp Filling
In a small bowl, combine the cornstarch with the lemon juice. Stir together with a fork until all of the cornstarch is dissolved. Add the sugar and the cinnamon to the cornstarch mixture and whisk it together until it's smooth.
Add the sliced pears to a large bowl. Pour the cornstarch mixture over the pears and gently stir until the pears are coated.
Pour the pear filling into the cast-iron skillet.
Cinnamon Streusel Topping
In a large bowl combine the brown sugar, flour, nutmeg, and oats. Stir together. Add the cold diced butter. Using a pastry cutter, cut the butter until crumbly.
Assemble & Bake
Generously spoon the streusel topping over the pear filling.
Bake for 30 to 35 minutes or until the topping is browned and the pear filling is bubbling through.
This recipe was calculated using the exact brands and measurements I used to make this recipe. If you are following a strict diet please note changing anything will cause the nutritional info to change. My calculations are intended as a guide only.