Preheat your oven to 350°F (175°C) and prepare a 9x5-inch loaf pan by greasing it with butter or oil and lightly flouring it.

In a medium mixing bowl, whisk together the all-purpose flour, sugar, baking soda, baking powder, salt, and cinnamon until well combined.

In a large mixing bowl, combine the milk and lemon juice, letting it rest for about 5 minutes. Then add the vegetable oil, vanilla extract, and eggs, whisking until smooth.

Gently fold the dry ingredients into the wet ingredients until just combined; be careful not to overmix.

In a small bowl, mix the brown sugar, cinnamon, and melted butter until well blended to create the cinnamon swirl.

Pour half of the batter into the prepared loaf pan and drizzle three lines of the cinnamon swirl mixture over it. Swirl gently with a skewer or knife.

Add the remaining batter on top and repeat the process with the remaining cinnamon swirl mixture. Swirl again lightly.

Bake in the preheated oven for about 50 minutes or until a toothpick inserted in the center comes out clean.

Allow the cinnamon bread to cool in the pan for 5-10 minutes before inverting it onto a wire rack to cool completely.