Instructions
Preheat the oven to 325℉ and prepare a bundt pan with shortening or butter and flour. Coat all the nooks and crannies.
Place the dry ingredients into a large bowl and stir with a fork.
Combine the buttermilk, lemon and vanilla into a smaller bowl.
In a third bowl, whisk the eggs and yolk.
Place the butter and sugar into your mixer and beat for three minutes on medium-high speed. Reduce the speed and add the eggs in two additions making sure that they have been incorporated completely. Alternate adding the flour and buttermilk mixtures to the bowl. 1/3 flour and 1/2 the buttermilk increments. Cover the bowl and set aside while preparing the blueberries.
For the Blueberry MarbleMix the sugar, pectin, and salt together and place into a medium pot.
Blend the blueberries until mostly smooth. You can use a food processor, immersion blender or just the back of a fork. Add 1/4 cup of the puree with the lemon zest and juice to the pot and cook over medium heat. Bring to just a simmer, the sugar and pectin should be completely dissolved. Remove from heat and allow to cool for five minutes.
Pour the remaining blueberry puree into the cooled mixture and whisk together.
For the Bundt CakePour half the cake batter into the prepared bundt pan. Use the back of a spoon to make a well in the batter (think of it like a moat in the middle). Spoon half the filling into the well and swirl it around with a knife. Add the remaining cake batter and repeat with the blueberry puree.
Bake for 60 to 70 minutes. The top should be golden an a skewer should come out clean.
Let cool for 10 minutes in the pan then invert it over a cooling rack and allow to completely cool before unmolding and serving.
To add the glaze, mix sugar, milk and vanilla and stir to combine. You can thin it our with more milk and less sugar. Top with additional blueberries and enjoy!