Preheat the oven to 325 degrees.

|| Coffee Cake || Cream together butter, sugar, vanilla extract, and eggs with an electric mixer. In a separate bowl, sift flour, salt, baking powder, and baking soda. Put half of the flour mixture into the butter and stir. Pour the buttermilk into the batter, and mix together for about 30 seconds, and then add the rest of the flour mixture. Mix until well incorporated. Fold in the blueberries and jam until just marbled. Pour into a well-oiled 9-inch cake round.

|| Crumble || Melt the butter and add flour, brown sugar, and cinnamon. Mix with your hands until mixture forms a crumble. Sprinkle crumble on top of the cake along with the blueberries, and dot with the blueberry jam. Bake in the oven for 45-50 minutes or until a toothpick inserted in the center comes out clean.

Serve warm or at room temperature.