Preheat your oven to 350°F (175°C) and prepare a 9x13 inch baking pan with nonstick spray.

In a large bowl, whisk together the all-purpose flour, baking powder, baking soda, chai spices, and salt.

In a separate bowl, beat together the eggs and granulated sugar until pale and fluffy. Add pumpkin puree, melted butter, buttermilk, and vanilla, mixing gently.

Fold the wet ingredients into the dry mixture until just combined; do not overmix.

Pour the batter into the prepared pan and bake for approximately 35 minutes or until a toothpick comes out clean.

Melt butter in a skillet over medium heat until golden brown and fragrant.

In a bowl, whisk together the browned butter, powdered sugar, and milk until smooth.

Once the cake is cool, frost the top with the brown butter frosting.

Slice into squares and serve at room temperature, optionally with chai or ice cream.