Line 8 wells of a 12 count muffin tin with paper liners or spray with cooking spray. Set aside.
CREAM CHEESE FILLING
In a small bowl using a handheld mixer, beat the cream cheese, sugar, and vanilla extract until smooth.
In a large bowl, sift together the flour, sugar, cocoa powder, baking powder, and salt. Set aside.
In a medium size bowl, whisk together the buttermilk, oil, egg, food coloring, and vanilla extract. Pour the wet ingredients into the dry ingredients and gently stir together with a spatula until everything comes together.
Using a Tablespoon measure, spoon 1 Tablespoon of muffin batter into the bottom of the 8 prepared wells. Using a second Tablespoon measure, spoon 1 scant Tablespoon of cream cheese filling on top of each mound of batter. Finally, add 1 and 1/2 Tablespoons of batter to each well, mostly covering the mound of cream cheese filling. If some is poking out, that's ok.
Bake the muffins for 5 minutes. After the 5 minutes is up, reduce the temperature to 350ºF without opening the door and bake another 10-12 minutes. A toothpick inserted in the center of a muffin should come out mostly clean (there will be cream cheese filling on it-- check for wet red batter).
Allow muffins to cool in the pan about 10 minutes so filling can set. Transfer to a wire cooling rack to cool completely before serving. Muffins are best on the day they are baked, but leftovers will last 3 covered tightly at room temperature up to 3 days or in the refrigerator up to 5 days. Muffins freeze well, up to 2 months. Thaw in refrigerator overnight.