Preheat oven to 350 degrees and grease a 9-inch by 5-inch loaf pan. Line with parchment paper and coat with nonstick spray.
In a small bowl combine 1/2 cup sugar and cinnamon. Set aside.
In a large bowl combine 1 cup sugar, 2 cups flour, baking powder, and salt. Set aside
In a medium bowl, beat egg with milk. Stir in oil. Add egg mixture to flour mixture and stir until combined. Batter will be lumpy.
Spoon 2/3 of the batter into the prepared baking pan. Sprinkle with half of the sugar mixture. Using a spatula or butter knife, cut through mixture and pull upwards to create a marbled look. Spoon remaining batter over top.
To the remaining sugar mixture, stir in 1/4 cup flour. Toss mixture with melted butter and sprinkle over the top of the batter in pan. Bake for 1 hour until a toothpick inserted comes out clean. Remove from the oven and cool in the pan for 10 minutes.
Using a sharp knife, slice around the inside of the loaf pan to loosen the cake and flip out onto a wire rack set over a baking sheet. Cool the cake completely.