Step 1: Prepare the Loaf Pan Preheat your oven to 350°F (177°C). Line a 9x5-inch loaf pan with parchment paper, leaving some overhang for easy removal, and spray with non-stick spray.
Step 2: Mix the Dry Ingredients In a medium bowl, whisk together the all-purpose flour, cocoa powder, baking soda, and salt. Set aside.
Step 3: Cream Butter and Sugar In the bowl of a stand mixer fitted with a paddle attachment, beat the unsalted butter and granulated sugar on medium speed until light and fluffy, about 3-4 minutes.
Step 4: Add Wet Ingredients Add the eggs one at a time, mixing on slow speed. Add the vanilla extract, red food coloring, sour cream, and white vinegar. Mix until smooth.
Step 5: Combine the Mixtures Gradually add the flour mixture to the wet ingredients, alternating with the buttermilk. Mix on low speed until just combined. Do not over-mix the batter or the cake will not be as tender!
Step 6: Bake the Loaf Cake Pour the red velvet batter into the prepared loaf pan and smooth the top with a butter knife. Bake for 50-60 minutes or until a toothpick inserted in the center comes out clean or use an instant-read thermometer to ensure it's at 210°.
Step 7: Cool the Cake Let the cake cool in the pan for 10 minutes, then transfer it to a wire rack to cool completely. Cream Cheese Frosting In a large mixing bowl, beat the softened cream cheese and butter together until smooth. Add the vanilla extract and powdered sugar, beating until creamy and fluffy.
Step 8: Assembly Once the cake is completely cooled, spread the cream cheese frosting evenly on top of the cake. Slice and serve!