Preheat oven to 350° F. Grease 3 (8-inch) round cake pans. Line with parchment paper, then butter.In a large bowl, beat together the coconut oil, yogurt, eggs, sugar, buttermilk, and vanilla. Add the flour, baking powder, baking soda, and salt. Mix until just combined. Fold in the raspberries and swirl in 3/4 cup raspberry jam, leaving a few streaks of jam throughout the batter, it shouldn't be fully incorporated.Divide the batter among the 3 cake pans and bake for 30-35 minutes, until the tops are just set and no longer wiggly in the center. Remove and let cool for five minutes. Run a knife around the edges of the pan and turn the cakes out onto a cooling rack. Cover and let the cakes cool completely before assembling.To make the frosting. In a bowl, beat together the butter and powdered sugar until light and fluffy. Add the melted white chocolate and vanilla, and beat until combined.To assemble, place one cake layer on a serving plate. Spread 1/3 of the frosting over the cake and layer with about 1/4 cup of jam. Repeat with the remaining cake layers. Be careful not to overfill your layers or the cake will be hard to slice. Lightly frost the outside of the cake, then decorate with smashed raspberries. Chill 30 minutes. Serve or store in the fridge for up to 3 days.