Preheat and prep: Heat your oven to 350°F (175°C). Grease an 8x8 or 9x9 baking pan or line it with parchment for easy lifting.

Mix dry ingredients: In a medium bowl, whisk flour, granulated sugar, baking powder, baking soda, and salt until well combined.

Combine wet ingredients: In a separate bowl, whisk egg, buttermilk, melted butter, and vanilla until smooth.

Make the batter: Pour the wet mixture into the dry ingredients. Stir gently with a spatula until just combined. The batter should be thick but spreadable. Do not overmix.

Make the swirl: In a small bowl, mix brown sugar, cinnamon, melted butter, and a pinch of salt until it forms a sandy paste.

Assemble the cake: Spread half the batter in the pan. Dollop half the cinnamon mixture over the batter. Swirl lightly with a knife. Repeat with the remaining batter and cinnamon, then swirl again. Keep the swirls loose—just a few figure-eights.

Bake: Bake for 25–32 minutes, depending on pan size. It’s done when a toothpick comes out with a few moist crumbs but no wet batter. The top should spring back lightly.

Make the glaze: While the cake bakes, whisk powdered sugar, milk or cream, vanilla, and a pinch of salt until smooth and pourable. Add more milk a teaspoon at a time if needed.

Glaze while warm: Let the cake cool for 10 minutes, then drizzle the glaze over the warm surface. It will melt into the swirls and set with a soft sheen.

Serve: Slice into squares and enjoy warm. For the full cinnamon roll vibe, serve with coffee or a cold glass of milk.