Preheat the oven to 350 F (177 C). Grease and line the bottom of a 9-inch (23 cm) springform or cake pan with parchment paper.

In a large bowl, whisk together the flour, baking powder, and salt until well combined.

In a large mixing bowl fitted with whisk attachment, whisk the sugar and lemon zest together until they have the consistency of wet sand.

On low, whisk the eggs and lemon sugar together until all the eggs are combined. Increase the speed to high and whip for 2 - 3 minutes until thick and light yellow.

With the mixture on low speed, stream in the olive oil, followed by the limoncello, lemon juice, and sour cream.

Mix for another minute on low to fully combine, scraping the sides and bottom of the mixing bowl as needed. On low, whisk in the dry ingredients until just incorporated.

Evenly pour the cake batter into the prepared pan. Bake for 35 - 45 minutes until a toothpick inserted into the center comes out clean or with a few moist crumbs.

Cool the cake in the pan for 15 minutes, then gently release the side of the springform pan, remove the ring, and allow the cake to cool completely to room temperature.

Place a mixing bowl and whisk attachment in the fridge or freezer for 15 - 20 minutes before making the frosting.

On low, whisk the mascarpone cheese until smooth. Mix in the vanilla extract and powdered sugar until well combined.

Slowly mix in the heavy cream on low speed. Once all the heavy cream has been added, increase the speed to medium for 2 - 3 minutes until the frosting is light and fluffy.

Once the cake is completely cooled, top with the mascarpone frosting, creating decorative swirls. Drop dollops of lemon curd into the swirls and gently swirl with the back of a spoon.