Gather 1 cup of fresh or frozen blueberries, 1 tablespoon of flour (to coat blueberries), 1 cup of unsalted butter (at room temperature), 1 cup of granulated sugar, 4 large eggs
Preheat your oven to 350°F (175°C). Coat the blueberries with 1 tablespoon of flour to prevent them from sinking to the bottom of the cake during baking. Set them aside.
In a large bowl, cream together the butter and granulated sugar until light and fluffy using a hand mixer or stand mixer.
Add the eggs one at a time, mixing well after each addition. Then, mix in the vanilla extract.
Gradually add the flour mixture to the butter mixture, alternating with the sour cream. Begin and end with the flour mixture, mixing until just combined.
Gently fold the flour-coated blueberries into the batter using a spatula until evenly distributed.
Pour the batter into a greased and floured 9x5-inch loaf pan. Smooth the top with a spatula.
Bake in the preheated oven for 60-70 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool in the pan for 10-15 minutes before removing it from the pan and transferring it to a wire rack to cool completely.