Preheat oven to 350°F (175°C). Grease or line a loaf pan with parchment paper.
In a large bowl, whisk together the flour, sugar, baking powder, and cinnamon.
In another bowl, mix the oil, eggs, and milk until smooth.
Add the wet ingredients to the dry ingredients and stir just until combined.
Fold in the diced apples.
Pour the batter into the prepared loaf pan and spread evenly.
In a small bowl, mix the sugar and cinnamon for the topping.
Sprinkle the cinnamon sugar evenly over the batter.
Bake for 45–55 minutes, or until a toothpick inserted into the center comes out clean.
Allow the loaf to cool in the pan for 10 minutes, then transfer to a wire rack.
Serving Suggestions
Serve warm with butter, honey, or a dusting of powdered sugar.