Preheat oven to 400 degrees.
Peel, pit, and slice pears. Add to a large mixing bowl.
Sprinkle brown sugar, sugar, corn starch, cinnamon, and lemon juice over pears.
Stir to coat evenly and let stand for 10 minutes.
Pour into an ungreased 13 x 9 baking dish.
Bake for 10 minutes, remove from oven, and set aside.
In a medium bowl, whisk flour, brown sugar, sugar, baking powder, and salt together.
Using a pastry blender, cut butter into flour mixture until mixture becomes crumbly.
Pour in boiling water and mix until combined.
Spoon mixture over pears and spread to cover entire dish.
Sprinkle coarse sugar on top.
Bake for 40-50 minutes or until topping is golden brown.