Preheat oven to 350°F (175°C). Grease and flour two 9-inch round cake pans, or line with parchment rounds.

Whisk together 2 1/2 cups flour, 1 1/2 tsp baking powder, 1/2 tsp baking soda, and 1/4 tsp salt in a bowl. Set aside.

In another large bowl, cream 1/2 cup softened butter with 1 1/2 cups granulated sugar until light and fluffy, about 3–4 minutes on medium speed. Add 3 eggs one at a time, mixing well after each. Stir in 1 tsp vanilla.

Add the dry ingredients to the butter mixture in three additions, alternating with 1 cup buttermilk: dry, buttermilk, dry, buttermilk, finish with dry. Mix until just combined — don’t overmix.

Fold in 1/2 cup melted (and cooled) white chocolate chips and 1 cup fresh raspberries gently so they don’t break up too much. Divide batter evenly between the prepared pans and smooth the tops.

Bake for 25–30 minutes, rotating pans once halfway, until the centers spring back slightly and a toothpick inserted in the center comes out clean.

Cool cakes in pans for 10 minutes, then invert onto a wire rack to cool completely before filling and frosting.

In a small saucepan combine 1 1/2 cups raspberries, 1/4 cup sugar, 1 Tbsp cornstarch, and 1 Tbsp lemon juice. Cook over medium heat, stirring, until it thickens and becomes glossy (about 3–5 minutes).

Cool completely; refrigerate to set. If you want seedless, press through a fine sieve.

Melt 1 cup white chocolate chips gently (double boiler or short bursts in microwave, stirring frequently). Let cool slightly.

Beat 1/2 cup softened butter until creamy, then add the melted white chocolate and beat until smooth.

Gradually add 3 cups powdered sugar and enough heavy cream (2–3 Tbsp) to reach spreadable consistency. Stir in 1 tsp vanilla.

Chill briefly if too soft.

Place one cake layer on a plate or cake board, spread the raspberry filling evenly (leave a small border to prevent overflow), and top with the second cake layer.

Crumb coat with a thin layer of frosting and chill for 15–20 minutes. Finish frosting and smooth.

Decorate with extra fresh raspberries or white chocolate shavings. Chill until ready to serve.