• For the cinnamon swirl, mix brown sugar and cinnamon together in a small bowl. Set aside.

For the Cake

• Preheat oven to 350°F. Grease a 9"x5" loaf pan, and line the bottom with parchment paper.
• In a large mixing bowl, whisk the flour, baking soda, and salt together.
• In a separate medium mixing bowl, whisk the egg and granulated sugar together until combined.
• Whisk in the oil, yogurt, milk, and vanilla extract.
• Pour the wet ingredients into the dry ingredients, then whisk until just combined. Avoid over-mixing.
• Pour and spread half of the batter into prepared loaf pan. Sprinkle the cinnamon swirl mixture evenly on top.
• Carefully pour and spread remaining batter evenly on top. The top layer of batter will stick to the cinnamon sugar filling, so spread very carefully.
• Using a knife, make a large swirl down the loaf pan, as shown in the video tutorial below. Avoid over-swirling, which will mix the layers together too much.
• Make the streusel topping: Combine the flour, brown sugar, and cinnamon, and stir to combine. Add the melted butter and mix until the mixture resembles wet sand and clumps together.
• Sprinkle the streusel evenly over the top of your bread.
• Bake at 350°F for 50-65 minutes, until cooked through, covering loosely with foil about halfway through to prevent the top from over-browning.
• Remove from the oven and allow the bread to cool in the pan set on a wire rack for 1 hour. After that, remove the bread from the pan and let it cool directly on a wire rack.

Vanilla Glaze

• In a medium mixing bowl, whisk all the glaze ingredients together until smooth. Drizzle on top of cake.