Preheat the oven to 350 F. Coat 1 standard size half baking sheet with no-stick baking spray and line with parchment paper.

Sift cake flour into a medium size bowl, add baking powder, salt, and baking soda and whisk until well mixed.

In a stand mixer, combine sugar and butter in a stand mixer and beat on high until well blended for about 2 minutes.

Reduce the mixer to medium and add 2 eggs and half the milk, scraping down the bowl when needed, repeat with remaining milk and eggs. While the mixer is still running, add vanilla extract.

On low, gradually add flour mixture over the course of 2 or 3 minutes, until fully combined. Make sure not to over mix. Gently fold in flour by hand if needed. It’s important not to overwork the batter at this stage.

Using an offset spatula, spread cake batter into an even layer across the surface of the prepared sheet pan. Use spatula to guide batter into the corners of the pan and make sure batter is evenly distributed across the pan. If using three cake pans, divide batter evenly into each pan.

Bake for 16-18 minutes. Cool and place on a wire rack. Cool completely before frosting. Cake can be frozen.

In a medium saucepan, whisk cornstarch, water, and sugar together. Add the fresh raspberries and cook on medium-high heat until the mixture boils. At a boil, stir and smash the raspberry mixture frequently with a rubber spatula, until the raspberries are completely smashed and all the seeds are visible, about 5-6 minutes, making sure the mixture doesn’t burn. Once at an almost jelly-like consistency, take off heat, and gently stir in vanilla. Let mixture completely cool.

The mixture can be made in advance and stored in the refrigerator for up to 4 days. The mixture will thicken the longer it rests, making it easier to spread into cake filling.

Place the room temperature butter in the bowl of a stand mixer, sift in powdered sugar, using the paddle attachment mix on low until powdered sugar is fully mixed. Add vanilla and salt and increase to medium speed until frosting forms and looks light and airy, pause mixing to scrape down the bowl to make sure all of the butter is incorporated, about 6 minutes.

Turn stand mixer speed to low and slowly drizzle in the milk, the buttercream mixture will start to look curdled at first, but it’s not. Keep mixing for 2-3 more minutes until buttercream appears silky. Taste for texture and flavor and keep mixing if lighter texture is desired. Use immediately or refrigerate until use.

For the bottom layer, make a buttercream dam along the perimeter of the bottom layer and fill in with raspberry filling. Place the second layer carefully on top, make a buttercream dam along the perimeter and add a thin layer of raspberry. Carefully place the third layer on top.

Spread a thin layer of frosting around the entire cake and top, this is your crumb coat. Refrigerate the cake for 10-20 minutes and then continue frosting, taking care to evenly spread out the frosting since this is the final coat.