Preheat oven to 350°F (175°C). Grease and flour your pan (6-cup bundt or 8-inch round).
In a small bowl, whisk together flour, baking powder, and salt. Set aside.
In a large mixing bowl, whisk together brown sugar and eggs until smooth and slightly thickened.
Stir in the spice blend.
Add oil and vanilla extract, mixing until fully combined.
Add the dry ingredients to the bowl in three parts, alternating with the buttermilk. Begin and end with the dry ingredients. Mix gently by hand until just combined—do not overmix.
Pour batter into the prepared pan.
Bundt pan: bake 35–40 minutes, until a toothpick comes out clean.
8-inch round pan: bake 28–30 minutes, until a toothpick comes out clean.
Let cake cool in the pan for 10 minutes before turning out onto a wire rack.
For dusting, combine powdered sugar and cornstarch, then sift over cooled cake.
Notes
Skip the store-bought buttermilk & just squeeze a lemon into 1 Cup of milk!