01 - Preheat the oven to 350°F (175°C). Grease and line an 8x4-inch loaf pan with parchment paper.
02 - In a large bowl, whisk together the flour, sugar, baking powder, salt, and cinnamon until evenly distributed.
03 - In a separate bowl, beat together the milk, eggs, melted butter, and vanilla extract until well combined.
04 - Pour the wet ingredients into the dry ingredients and stir gently until just combined. Be careful not to overmix.
05 - In a small bowl, mix together the brown sugar and cinnamon for the filling layer.
06 - Pour half of the batter into the prepared loaf pan. Sprinkle the cinnamon sugar mixture evenly over the batter. Pour the remaining batter on top and smooth the surface with a spatula.
07 - Bake for 40–50 minutes, or until a toothpick inserted into the center comes out clean.
08 - Let the loaf cool in the pan for 10 minutes, then transfer to a wire rack. While still warm, brush the top with melted butter and sprinkle with the cinnamon sugar topping.
09 - Allow the loaf to cool completely before slicing into 8 even pieces.