Preheat your oven to 350°F (175°C) and grease a 9 x 5-inch loaf pan.

In a medium bowl, whisk together all-purpose flour, sugar, baking soda, baking powder, salt, and cinnamon.

In a large bowl, whisk together the milk and lemon juice, let it stand for 5 minutes, then blend in vegetable oil, vanilla extract, and eggs.

Gradually add the dry mixture to the wet ingredients in three parts, stirring gently.

In a small bowl, combine brown sugar and cinnamon with melted butter to create the cinnamon swirl.

Pour half of the batter into the greased pan and add three lines of the cinnamon swirl mixture.

Add remaining batter and repeat with the remaining cinnamon mixture, then bake for about 50 minutes.

Remove from the oven and let cool for 5-10 minutes before inverting onto a cooling rack.