Preheat oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
In a large bowl, cream butter and sugar until light and fluffy, about 3-4 minutes.
Add eggs one at a time, beating well after each addition. Mix in vanilla extract.
Stir in melted white chocolate.
Add flour mixture in three parts, alternating with milk, beginning and ending with flour. Mix until just combined.
Fold in chopped toasted pecans.
Divide batter evenly between prepared pans. Smooth tops with a spatula.
Bake for 30-35 minutes, or until a toothpick inserted comes out clean.
Let cakes cool in pans for 10 minutes, then turn out onto wire racks to cool completely.
For frosting, beat butter until creamy. Add melted white chocolate and beat until smooth.
Add powdered sugar, vanilla, salt, and raspberry puree. Beat until fluffy and spreadable.
Place one cake layer on a serving plate. Spread frosting on top.
Add second cake layer. Frost top and sides with remaining frosting.
Decorate with extra pecans or fresh raspberries if desired.