Preheat oven to 350F. Spray a 9x5 loaf pan with non-stick cooking spray; set aside.
In a large mixing bowl combine the flour, baking powder, salt, and ¾ cup sugar.
In a separate large mixing bowl, whisk together the egg, milk, vanilla, and sour cream.
Pour the dry ingredients into the wet and mix until combined.
Pour batter into the prepared loaf pan.
In a small bowl combine the 1/2 cup of sugar, 3 teaspoons cinnamon and 2 tablespoons melted butter. Spoon the cinnamon crumble mixture over the batter and use a knife and swirl it into the bread a bit.
Bake the bread for 45-50 minutes or until a toothpick comes out clean.
Remove the bread from the oven and cool in the pan on a cooling rack for 20 minutes. Remove the bread from the pan.
In a small bowl, combine the powder sugar, milk, and vanilla then drizzle the frosting over top of the bread.