Preheat your oven to 350°F and grease a 9-inch round cake pan, then line the bottom with parchment paper. This prevents sticking and ensures clean cake release after cooling completely.

Whisk together flour, baking powder, and salt in a small bowl, setting the dry mixture aside. Combine lemon juice and zest in a separate cup, letting the zest absorb the juice's moisture for maximum flavor.

In a large mixing bowl, cream softened butter and granulated sugar together for 3-4 minutes until pale and fluffy. Add eggs one at a time, beating well after each addition, then stir in vanilla extract.

Alternate adding the flour mixture and sour cream to the butter mixture, beginning and ending with flour—add about one-third flour, then half the sour cream, then one-third flour again, then remaining sour cream, finishing with final flour portion. Gently fold in the lemon juice and zest using a rubber spatula, being careful not to overmix.

Toss fresh blueberries lightly with 1 tablespoon of flour, then gently fold them into the batter just before pouring. This prevents berries from sinking to the bottom during baking.

Pour the batter into your prepared pan and bake for 35-40 minutes until a toothpick inserted in the center comes out with a few moist crumbs attached. The cozy summer lemon blueberry cake recipe is done when the top springs back lightly when touched.

Cool the cake in the pan for 15 minutes, then turn out onto a wire rack to cool completely before glazing. While cooling, whisk together powdered sugar, milk, and the additional lemon juice until smooth.

Drizzle the lemon glaze over the cooled cake, letting it pool naturally along the edges and center. Allow the glaze to set for at least 10 minutes before slicing.