Step 1

Preheat oven to 350 degrees. Butter and flour a 9 inch round baking pan.Place the room temperature butter, white sugar in a large bowl. Beat the two ingredients together with an electric mixer on high speed for 4 - 5 minutes until the ingredients are light and fluffy.Reduce the mixer to low speed and add the eggs one at a time, beating well after each addition. Add the vanilla, lemon zest and sour cream to the bowl. Beat everything together until it’s well incorporated. In a separate medium size bowl sift the flour, baking powder, baking soda and salt together.  With the mixer on low speed add the sifted dry ingredients to the batter and mix just until the ingredients are incorporated.Fold the fresh blueberries into the batter. Spoon the batter into your prepared pan. Spread it out evenly. (You can coat the blueberries with 1 Tablespoon of flour to keep them from sinking to the bottom.)Crumble the topping evenly over the top of the batter. Bake at 350 degrees for 40 - 50 minutes or until it tests done when a toothpick is inserted in to the center. Cool completely on a wire rack.

Step 2

Crumb Topping

Step 3

Combine the granulated sugar, brown sugar, cinnamon, and nutmeg in a bowl. Stir in the melted butter and then the flour. Mix well and set aside to top the cake batter with before baking.