For the crumble, add all of the ingredients to a bowl and mix it together, either by hand using a fork or with an electric mixer, until a crumble structure and there is no dry flour left. Set it aside while preparing the cake.

Preheat the oven at 175ºC/350ºF conventional oven and prepare a 23 cm/9-inch springform with parchment paper.

Sift together the all-purpose flour, baking powder and salt and set it aside.

In a large bowl using an electric hand mixer or in a bowl of a stand mixer, add the butter, lemon zest and granulated sugar and mix it on high speed for 3 minutes.

Add the eggs one at a time into the mixture and on low speed mix it in until combined.

Continue by adding half the dry ingredients, on low speed, mixing until just combined.

Then add the lemon juice, sour cream, vegetable oil, vanilla extract and mix until just combined. Then add the other half of the dry ingredients and mix until combined.

Toss the clean and dry raspberries in the cornstarch. Add half of them into the cake batter, and gently fold them in, using a rubber spatula.

Add the cake batter into the prepared cake pan and top it with the remaining raspberries. Finally top it with the crumble.

Bake it for 45-55 minutes or until the cake tester comes out clean. Once baked, let the cake cool. After 10 minutes, gently drag a thin knife along the edge of the cake to release the cake from the springform. Let it cool down completely on a wire rack.

Stir together all of the ingredients until smooth. Drizzle it over the cake and it’s ready to be served.