Preheat your oven to 350 degrees, and generously grease a 9-inch loaf pan. Set aside. 

In a medium bowl, whisk together the flour, spices, baking powder, and salt. Set aside. 

In a large bowl, beat together the butter, oil, and sugar until fluffy. Add in the eggs, one at a time, and the vanilla extract. Add in the dry ingredients alternating with the buttermilk until all ingredients have been added. The batter will be thick and smooth. Pour into your prepared pan, and bake for 35-40 minutes, or until a cake tester comes out clean. 

Cool the cake completely before slicing and frosting. 

In a small saucepan, whisk together the flour, milk, salt, and cinnamon until combined. Cook over medium-high heat, whisking frequently, for about 5-10 minutes, or until the mixture becomes very thick and paste-like. Remove from heat, and place in a bowl to cool. Cool the mixture completely before moving on- this is very important! 

In the bowl of a stand mixer, beat together the butter and sugar until it becomes very light in color- almost white- and very fluffy. This will take about 10 minutes on medium speed, using the paddle attachment. 

Once the flour mixture is cool, beat it into the butter mixture on high, and let the mixture beat for another 5 minutes or so. The frosting will become very light and fluffy and smooth. Add in the vanilla extract and beat to combine. Then, frost your cake as desired!