Step-by-Step Instructions
Part 1: Prepare the Cinnamon Swirl
Combine Swirl Ingredients: In a small bowl, whisk together the brown sugar, ground cinnamon, and 1 tablespoon of flour.
Add Butter: Pour in the 2 tablespoons of melted butter and mix until the mixture resembles coarse, moist crumbs. Set this aside.
Part 2: Make the Loaf Cake Batter
Prep Oven and Pan: Preheat your oven to $175^{\circ}\text{C}$ ($350^{\circ}\text{F}$). Grease and flour a standard 9×5 inch loaf pan or line it with parchment paper, leaving an overhang on the long sides for easy removal.
Mix Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, and salt.
Cream Butter and Sugar: In a large bowl or a stand mixer, beat the softened butter and granulated sugar together on medium speed until the mixture is light and fluffy (about 3-5 minutes).
Add Wet Ingredients: Beat in the eggs, one at a time, mixing well after each addition. Stir in the vanilla extract. Scrape down the sides of the bowl.
Alternate Wet and Dry: Reduce the mixer speed to low. Gradually alternate adding the flour mixture and the milk (or buttermilk), starting and ending with the flour. Mix only until just combined; do not overmix.
Part 3: Layer, Swirl, and Bake
First Layer: Spoon half of the cake batter into the prepared loaf pan and spread it into an even layer.
Cinnamon Swirl: Sprinkle about two-thirds of the prepared cinnamon swirl mixture evenly over the batter layer.
Top Layer: Gently spoon the remaining cake batter over the cinnamon filling. Use an offset spatula to spread it carefully without disturbing the layer underneath too much.
Final Topping: Sprinkle the remaining cinnamon swirl mixture over the top of the batter.
Bake: Bake for 50 to 65 minutes, or until a wooden skewer or toothpick inserted into the center (avoiding the densest part of the swirl) comes out clean or with just a few moist crumbs attached.
Cool: Let the loaf cool in the pan for 10-15 minutes, then use the parchment paper overhang to lift it out and transfer it to a wire rack to cool completely.
Part 4: The Vanilla Glaze
Mix Glaze: In a small bowl, whisk together the sifted powdered sugar, vanilla extract, and 2 teaspoons of milk/cream until smooth. Add the remaining milk/cream, a drop at a time, until the glaze reaches your desired drizzling consistency.
Drizzle and Serve: Once the cake is completely cool, drizzle the vanilla glaze back and forth across the top of the loaf. Let the glaze set for 10 minutes before slicing and enjoying!
