Preheat your oven to 350°F/175°C. Generously butter your bundt pan using a pastry brush and softened butter (or you could use a spray), making sure you get every bit of the pan
In a stand mixer fitted with the paddle attachment, cream together the butter, sugar and salt for 2-3 minutes until fluffy
Add the eggs one at a time, beating well after each one. Scrape the bowl with a rubber spatula after each one. Add the vanilla.
Whisk together the flour and baking powder. Add the dry ingredients in three additions, alternating with the buttermilk. Start and end with the dry ingredients
Scoop out ½ cup of batter and place it into a small bowl. Mix in the jam and whisk until smooth.
Fold in the white chocolate chips with the rest of the batter.
Pour half of your batter into the bundt pan.
Use a spoon to pour in the raspberry batter, making sure it stays in the middle of the batter and doesn't touch the sides (otherwise you'll see it on the outside of the cake once it's baked, this way it stays more 'hidden' until you slice into it)
Pour over the rest of the batter. Bake for 45-60 minutes.If your bundt pan is a dark metal it will take about 45 minutes, but it will take 10-15 minutes longer if your pan is a light metal.
A toothpick inserted will come out with no crumbs. Let it cool for 10 minutes, then place a cooling rack on top of the pan. With your oven gloves on, flip the cake pan so now the cooling rack is on the bottom. Carefully lift your bundt pan off. Let cool completely.
Place your white chocolate in a heat proof bowl. In a small saucepan, bring your heavy cream to a simmer. Pour over your white chocolate and leave for a minute. Take a rubber spatula and slowly mix it until the white chocolate has completely melted. Add in your butter and continue stirring. You'll have to leave it until it is the consistency you want - either very pourable and like a glaze or until very thick.
Notes
Butter: I use European style butter, like Kerry Gold, in my recipes. This will make your finished bake much creamier and richer.Storage: Keep your cake covered at room temperature for up to 4 days. Pouring Ganache: The best way to pour ganache is to pour it into a jug, and then pour on top of the cake. I like to put my cake on a stand and slowly turn the stand while pouring. Freezing: Slice the cake without the ganache, wrap tightly and freeze for up to 2 months. Let it thaw out in the fridge before serving.