Chocolate and Vanilla Red Velvet Cake
*Test kitchen tip
To make 1-1/2 cups sour milk, place 4-1/2 teaspoons lemon juice or vinegar in a glass measuring cup. Add enough milk to make 1-1/2 cups total liquid; stir. Let the mixture stand for 5 minutes before using.
**Test kitchen tip
If you have only one square pan, bake one layer at a time. Cool cake as directed in pan, then turn onto a wire rack. Wash and dry the pan. Grease and flour. Repeat baking each layer. Store cake batter in the refrigerator until ready to bake.
To make ahead:
Prepare as directed through Step 3. Place cakes in an airtight container; cover. Store at room temperature for up to 3 days or freeze for up to 1 month. Thaw cakes, if frozen. Continue as directed in Step 4.