For the Cake:

1. Preheat oven to 350° F. Grease and flour a bundt pan.
2. Rinse and dry blueberries. Coat blueberries with 1/4 C flour by mixing with a spoon.
3. Butter should be at room temperature or slightly firmer, not melted. Combine sugars with softened butter. Beat on medium speed until butter and sugar are well combined, light, and fluffy.
4. Add eggs, one at a time, beating each egg into the butter and sugar one at a time.
5. After mixing both eggs, add vanilla, sour cream, lemon zest, and lemon juice. Beat on medium speed until well combined.
6. In a separate bowl, Sift flour and then measure out 2 cups. Add salt and baking powder. Stir to combine. Slowly add the flour mixture to the batter and mix on low speed until just combined. The batter will be thick.
7. Fold blueberries into batter.

For the Streusel:

1. Melt butter in the microwave, for about 30 seconds.
2. Combine all dry ingredients in a medium-sized bowl. Pour melted butter over dry ingredients and stir until well mixed. This mixture will be clumpy.

To Assemble:

1. Pour the batter into the pan. Cover the bottom with streusel.
2. Bake at 350° F for 50-55 minutes. The bottom of the cake will be slightly brown. Use a long toothpick or knife to stick in the middle of the cake. If it comes out clean, the cake is done.
3. Set on a cooling rack for twenty minutes.
4. Place a plate, cutting board, or other flat surface; over the cake and hold it together. Turn the cake over and gently pat the sides of the pan until the cake comes loose. Allow to cool for another 15-20 minutes.