Bread:
2 cups all-purpose flour
1 cup white sugar
1 cup buttermilk
2 large eggs
¼ cup vegetable oil
2 teaspoons vanilla extract
2 teaspoons baking powder
1 ½ teaspoons ground cinnamon
1 teaspoon salt
½ teaspoon baking soda
Topping:
2 tablespoons white sugar
2 teaspoons butter or margarine
1 teaspoon ground cinnamon
Preheat the oven to 350 degrees F (175 degrees C). Generously grease a 9x5-inch loaf pan.
To make the bread: Beat flour, sugar, buttermilk, eggs, oil, vanilla, baking powder, cinnamon, salt, and baking soda in a large mixing bowl until well combined, about 3 minutes. Pour batter into the prepared loaf pan; smooth the top.
To make the topping: Stir sugar, butter, and cinnamon together in a small bowl until crumbly; sprinkle over batter. Use a paring knife to swirl batter for a marbled effect.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 50 minutes. Remove bread from the pan to a wire rack to cool completely.