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.
220 g all-purpose flour, 1 ½ teaspoon baking powder, ¼ teaspoon salt
In a large bowl, add lemon zest and granulated sugar, and rub it together to release all of the lemon zest flavor, until it looks like wet sand. Then add the butter and mix it on high speed using an electric hand mixer or a stand mixer, for 3 minutes.
150 g granulated sugar, 1 tablespoon lemon zest, 85 g butter
Add the eggs one at a time into the mixture and on low speed mix it in until combined.
2 large eggs
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.
1 tablespoon lemon juice, 150 g sour cream 14-18%, 25 g vegetable oil, 1 teaspoon vanilla extract
Add the cake batter into the prepared cake pan and even it out. Then top it with the lemon curd, and spread into an even layer. Finally top it with the crumble.
Bake it for 45-50 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.