Preheat the oven to 350F degrees.
Grease a 9" round springform pan with nonstick cooking spray or use flexipan. Set aside.
In a medium bowl, make the streusel by combining flour, sugars & cinnamon & 1/2 cup butter cut into chunks.
Cut butter into dry ingredients using a pastry cutter or by crossing 2 knives until the mixture is crumbly. Set aside.
Make the cake batter by combining flour, baking powder & salt in a large bowl. Set aside.
Combine & beat together in large mixer bowl butter & sugar on medium speed until fluffy
Add in the eggs & vanilla, continue beating until combined.
Fold in sour cream.
Carefully add in flour mixture & buttermilk. Beat well.
Pour batter into the prepared pan.
Place spoonfuls of preserves on top of the cake batter & cut a knife through to create swirls. Sprinkle the streusel on top
Bake in your prepared oven for 50 to 60 minutes, or until toothpick test is clean.
Make the glaze, whisk together the milk & confectioners sugar until a smooth
Drizzle cake with glaze.