Crispy Grape Streusel Pie

Preheat the oven to its highest temperature setting, 425 degrees Fahrenheit or 220 degrees Celsius. Position a baking sheet on the lowest oven rack to accommodate the pan.

Gently twist and release each grape, separating its skin from its pulp. Set the skins apart from the pulp. Transfer the pulp to a medium-sized saucepan and bring it to a rolling boil, stirring constantly for 1 minute. Pass the mixture through a fine-mesh strainer or food mill to remove any seeds.

In a separate bowl, mix the pulp, skins, granulated sugar, all-purpose flour, freshly squeezed lemon juice and a pinch of salt. Pour this mixture into the pre-made pastry crust.

In another bowl, combine rolled oats, brown sugar and all-purpose flour. Use your fingers or a pastry blender to work in the butter until you achieve a crumbly texture. Sprinkle this mixture evenly over the filling.

Cover the edges of the pastry with aluminum foil to prevent over-browning. Place the baking sheet in the oven and bake for 15 minutes. Remove the foil, and continue baking for an additional 20 minutes or until the pastry is golden brown and bubbly. Allow it to cool completely on a wire rack.