In a mixing bowl, combine the 120 g all-purpose flour, 1/2 tsp. baking powder, and ¼ tsp. salt.
Add the cold, cubed 75 g unsalted butter and mix using your hands until the mixture resembles coarse crumbs (about the size of peas). Gradually add the 45 ml cold water and mix again until the dough just begins to come together. Shape it into a disc.
On a floured surface, roll out the dough to fit your tart pan. Carefully transfer the rolled dough a cake pan with parchment paper and press it into the bottom and up the sides. Refrigerate the crust for 30 minutes.
The Raspberry
In a mixing bowl, combine the 100 g sugar and 1 Tbsp. cornstarch. Add the washed 300 g fresh raspberries and gently toss to coat.
The Crumble
In another mixing bowl, combine the 75 g rolled oats, 30 g all-purpose flour, and 50 g sugar. Add the melted 60 g unsalted butter and mix until the dry ingredients are moistened and clump together when pressed.
The Baking
Place the oven rack in the lowest position and preheat the oven to 400 °F (200 °C). Spoon the raspberry mixture into the chilled crust.
Evenly sprinkle the crumble mixture over the raspberry filling.
Place the tart in the preheated oven and bake for 35 minutes, or until the crumble is golden brown and the raspberry filling is bubbling at the edges.
Allow the tart to cool on a wire rack for at least 3 hours before serving. I usually place a small cloth on it.
The Serving
Serve your Raspberry Crumble Tart [Tarte crumble aux framboises] with a fresh cup of tea or coffee.