Make the Topping by stirring the sugar into the sour cream until well combined. Stir in the 1 teaspoon lemon juice if you'd like to make the topping a little tart. Cover and refrigerate until ready to use.
Preheat oven to 400°F Wash and drain blueberries. In a 1 1/2-quart baking dish or pan, mix together the blueberries, sugar, 1 tablespoon lemon juice and the lemon rind. Spread mixture evenly in dish.
In a bowl, mix graham-cracker crumbs and melted butter; spread evenly over blueberries. Bake on lower rack of oven for 35 to 40 minutes, until the buttered crumbs are lightly brown. Serve warm, adding the topping at the last minute.