Ingredients:

  • 3 cups (375g) all-purpose flour
  • 1.5 cups (300g) granulated sugar
  • 4 tsp baking powder
  • 0.5 tsp salt
  • 1.5 cups (355ml) whole buttermilk, room temperature
  • 2 large eggs, room temperature
  • 2 tsp pure vanilla extract
  • 0.5 cup (113g) unsalted butter, softened
  • 1 cup (225g) unsalted butter, melted and slightly cooled
  • 1 cup (200g) light brown sugar, packed
  • 2 tbsp all-purpose flour (for swirl)
  • 1.5 tbsp ground Saigon cinnamon
  • 4 oz (113g) full-fat brick cream cheese, softened
  • 0.25 cup (56g) unsalted butter, softened (for frosting)
  • 1.5 cups (180g) powdered sugar
  • 1 tsp vanilla bean paste
  • 3 tbsp whole milk

Instructions:

  1. Preheat your oven to 350°F (175°C) and grease your 9x13 pan.
  2. In your mixer, beat the 0.5 cup softened butter and 1.5 cups granulated sugar until light and fluffy. This takes about 3 full minutes — don't rush it.
  3. Add the eggs one at a time, followed by the vanilla. Slowly pour in the buttermilk while mixing on low speed. It might look slightly curdled, but that is just the acid reacting; it will smooth out once the flour is added.
  4. Whisk the 3 cups flour, baking powder, and salt together. Gradually add this to the wet ingredients until just combined. Overmixing at this stage will lead to a tough, bready cake.
  5. In a separate bowl, whisk the 1 cup melted butter, 1 cup brown sugar, 2 tbsp flour, and 1.5 tbsp cinnamon. Whisk until the mixture is glossy and thick.
  6. Spread the cake batter into the prepared pan. Drop dollops of the cinnamon mixture over the top. Use a knife to swirl the two together in a figure eight pattern. Note: Don't over swirl, or you'll just end up with a brown cake rather than distinct ripples.
  7. Slide the pan into the oven and bake for 35 minutes until a toothpick comes out with just a few moist crumbs.
  8. While it bakes, whip the cream cheese, 0.25 cup butter, powdered sugar, vanilla bean paste, and milk until silky and pourable.
  9. Let the cake cool for about 10 minutes. Pour the glaze over the warm cake so it seeps into the cinnamon crevices. Note: If the cake is too hot, the frosting will melt into a puddle; if it's too cold, it won't settle into the swirls.