Start by preparing the blackberry puree. In a medium saucepan, combine half of the Driscoll's blackberries, 1 tablespoon of fresh lemon juice, and ¼ cup of granulated sugar. Cook over medium heat for about 5 to 7 minutes, stirring gently until the mixture bubbles and the blackberries break down. Once done, remove from heat and let it cool slightly before blending until smooth. Set aside.

Preheat your oven to 350°F (175°C) and generously grease a bundt pan. In a mixing bowl, beat together 1 cup of unsalted butter and 1 ½ cups of granulated sugar until the mixture is light and fluffy, about 3 to 5 minutes. Add 4 large eggs, one at a time, ensuring each is fully incorporated.

In a separate bowl, whisk together 2 cups of all-purpose flour, 1 teaspoon of baking soda, and ½ teaspoon of salt. Gradually add this dry mixture to the butter mixture, alternating with 1 cup of room-temperature sour cream. Mix until combined.

Pour half of the cake batter into the prepared bundt pan, then swirl in half of the blackberry puree. Pour the remaining batter on top, followed by the rest of the blackberry puree. Swirl gently with a knife.

Bake for about 70 to 90 minutes, or until a toothpick inserted into the center comes out clean. Allow to cool in the pan for about 20 minutes before inverting onto a wire rack.

While the cake cools, prepare the glaze by whisking together 1 cup of confectioners sugar and enough whole milk to create a smooth consistency. Once the cake is cool, pour the glaze over the top.