1. Preheat the oven to 350°F. Butter a 9x13-inch baking pan and line it with parchment paper, leaving some overhang for easy removal.
2. In a large bowl, beat the butter and sugar. Add the sour cream and beat until fully combined, scraping down the sides of the bowl as needed. Reduce the speed to low, then add the eggs one at a time, ensuring each is fully incorporated before adding the next. Mix in the vanilla extract, lemon zest, and lemon juice.
3. In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Spread the batter evenly into the prepared pan and smooth the top with a spatula. Bake for 35-45 minutes, or until a toothpick inserted into the center comes out clean and the top is lightly golden brown. Let the cake cool in the pan on a wire rack for at least 30 minutes before lifting it out using the parchment paper overhang.
4. While the cake cools, prepare the frosting. Puree the raspberries in a blender until completely smooth, about 1-2 minutes. Strain the puree through a fine-mesh strainer into a small bowl, pressing firmly with a spoon to extract as much liquid as possible. You should have about 4 to 6 tablespoons of raspberry puree.
5. In a mixing bowl, beat the butter and cream cheese together on medium speed until fluffy, about 2 minutes. Gradually beat in the powdered sugar and salt on low speed then turn the mixer to high speed and whip for 2 more minutes until light and fluffy. With the mixer on low, add the raspberry puree one tablespoon at a time, whipping until fully incorporated and smooth. Use up to roughly 4 to 5 tablespoons of the puree. If the frosting looks curdled or separated,
continue whipping until it becomes fluffy.
6. Once fully cooled, carefully slice the cake in half horizontally with a serrated knife to create two even layers. Spread roughly 1 1/2 cups of frosting evenly over the bottom layer. Sprinkle with 2/3 cup crushed Loacker Quadratini for added crunch, then carefully place the top layer of cake over the filling.
7. Spread the remaining frosting evenly over the top of the cake. Decorate with fresh raspberries and assorted Loacker Quadratini. Cut and serve immediately, or cover and refrigerate for later. If refrigerating, bring the cake to room temperature for 30 minutes before serving for the best texture.