Preheat the oven to 350 degrees Fahrenheit (180 degrees Celsius). Line a 9X5-inch loaf pan with parchment paper. Leave 2 inches of paper hanging over the sides so the loaf is easy to remove.
In a large bowl, combine all purpose flour, granulated sugar, cocoa powder, baking powder, and salt on low speed with a hand mixer or stand mixer fitted with a paddle attachment.
210 grams all purpose flour, 200 grams granulated sugar, 3 tablespoons cocoa powder, 1 teaspoon baking powder, 1 teaspoon salt
Beat softened butter into the dry ingredients until the texture is grainy like wet sand.
226 grams unsalted butter
In a separate small bowl, whisk the eggs, sour cream, buttermilk, vanilla, vinegar, and food coloring together.
3 large eggs, 60 grams sour cream, 60 grams buttermilk, 2 teaspoons vanilla extract, ¼ teaspoon white vinegar, 2 teaspoons red gel food coloring
With the mixer on low speed, pour half of the wet ingredients into the dry. The batter should be thick and paste-like.
Scrape down the sides of the bowl with a rubber spatula, then stream in the remaining wet ingredients. It should look like pancake batter. It's ok if there are a few lumps.
Pour the batter into the prepared pan. Bake for 60-70 minutes or until a toothpick inserted in the center comes out clean with moist crumbs attached.
Remove from the oven the loaf cool in the pan for 5-10 minutes, then transfer to a wire rack to cool completely.
Cream Cheese Frosting
Beat the softened butter and cream cheese together with a mixer on medium-high speed until smooth and creamy.
Gradually add the powdered sugar to the mixture, one cup at a time, mixing well on low speed after each addition.
240 grams powdered sugar
Add the vanilla and salt. Mix on low until combined, then increase to medium until the frosting is fluffy
½ teaspoon vanilla extract, ⅛ teaspoon salt
Once completely cool, spread the frosting on top of the loaf cake. Garnish with cake crumbs or sprinkles. Enjoy!
Notes
Measuring dry ingredients: Measure the flour and cocoa powder in grams with a kitchen scale for the most accurate results. Fluff up the flour and gently spoon it into your measuring cup if you don't have a scale. Don't pack the flour in.Room temperature ingredients: Use room temperature dairy ingredients and eggs. Take them out of the fridge 1-2 hours before making the loaf.Storage: Store unfrosted in an airtight container on the counter for up to 4 days. If frosted, store in the fridge for up to 5 days.