Prepare the Sweet Potato

• Preheat the oven to 350°F (175°C).
• Grease a 9 × 13-inch baking pan and lightly dust it with flour.
• Cook the sweet potato until completely tender, then mash until smooth. Allow it to cool before using.

Make the Cake Batter

• In a large bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, and nutmeg.
• In another bowl, whisk the granulated sugar, brown sugar, eggs, vegetable oil, milk, vanilla extract, and mashed sweet potato until smooth.
• Gradually add the dry ingredients to the wet mixture.
• Stir gently until just combined. Avoid overmixing to keep the cake soft and tender.

Prepare the Cinnamon Swirl

• In a small bowl, combine the brown sugar, flour, cinnamon, and melted butter.
• Mix until the ingredients form a thick, crumbly paste.

Assemble the Cake

• Pour half of the cake batter into the prepared baking pan and spread it evenly.
• Sprinkle the cinnamon mixture over the batter, distributing it evenly.
• Spoon the remaining cake batter over the cinnamon layer and gently spread it to cover the filling.
• Use a butter knife to make a few gentle swirls through the batter without mixing the layers completely.

Bake the Cake

• Bake for 35–45 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
• Remove the cake from the oven and allow it to cool for about 15 minutes.

Make the Vanilla Glaze

• Whisk the powdered sugar, vanilla extract, and 2 tablespoons of milk until smooth.
• Add a little more milk if needed to reach a pourable consistency.
• Drizzle the glaze evenly over the slightly warm cake.