Preheat oven to 350 degrees Fahreinheit and spray a 8x8 or a 9x9 inch can pan or casserole dish with non-stick spray.
In a medium size bowl, add flour, sugar, salt, and cinnamon .
In another small bowl, beat egg then add milk, sour cream, oil and vanilla. Whisk to combine.
Add wet ingredients into dry ingredients and stir until combined. You'll still have some lumps, this is ok.
Fold in blueberries.
Bake 22 to 27 minutes, depending on your oven, watch cake carefully. Cake is done with a wooden pick inserted in center comes out clean.
Remove from oven and allow to cool 5 to 10 minutes before inverting onto a wire rack. Serve warm or room temperature.
Cake is good served warm with butter. You can also dust with confectioners sugar or drizzle with a glaze of 1 cup confectioners and 3 tablespoon milk (combine and stir until smooth)