Preheat your oven to 350°F (175°C). Grease and flour two 8-inch round cake pans. Line the bottoms with parchment paper circles. This prevents sticking and ensures easy release.

In a large bowl, whisk together the flour, granulated sugar, baking powder, and salt. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment (or using a hand mixer), cream the softened unsalted butter on medium speed until light and fluffy, about 2-3 minutes.

Add the eggs one at a time, beating well after each addition until fully incorporated. Scrape down the sides of the bowl as needed.

In a separate small bowl, whisk together the whole milk and vanilla extract.

With the mixer on low speed, gradually add the dry ingredients to the wet ingredients, alternating with the milk mixture. Begin and end with the dry ingredients (e.g., dry, wet, dry, wet, dry). Mix until just combined, being careful not to overmix.

Gently fold in the fresh raspberries using a rubber spatula. Distribute the batter evenly between the two prepared cake pans.

Bake for 30-35 minutes, or until a wooden skewer inserted into the center of the cakes comes out clean. The tops should be golden brown and spring back when lightly touched.

Remove the cakes from the oven and let them cool in the pans on a wire rack for 10-15 minutes. Then, carefully invert them onto the wire racks to cool completely. Do not frost warm cakes.

In the bowl of a stand mixer fitted with the paddle attachment (or using a hand mixer), beat the softened unsalted butter on medium-high speed until creamy and pale, about 3-4 minutes.

Gradually add the sifted powdered sugar, 1 cup at a time, beating on low speed until combined, then increasing to medium-high. Continue until all sugar is incorporated.

Add the fresh lemon juice, lemon zest, vanilla extract, and pinch of salt. Beat on medium-high speed for another 3-5 minutes, until the buttercream is light, fluffy, and smooth. If it's too thick, add a tiny bit more lemon juice (1/2 tsp at a time); if too thin, add more powdered sugar.

Once the cakes are completely cool, use a serrated knife to level the tops of the cakes if necessary, creating flat surfaces.

Place one cake layer on your serving plate or cake stand. Spread about 1 cup of lemon buttercream evenly over the top.

Carefully place the second cake layer on top. Apply a thin 'crumb coat' of buttercream over the entire cake (top and sides) to trap any loose crumbs. Refrigerate for 15-20 minutes to set the crumb coat.

Remove the cake from the fridge and apply the remaining buttercream to the top and sides, smoothing it with an offset spatula or palette knife to your desired finish.

Garnish the cake with fresh raspberries and thin lemon slices or extra lemon zest, if desired.