Fill two small disposable piping bags with different colored or flavored frosting. Use scissors to snip holes in the bottoms of both bags. Insert both bags into a large (16”) disposable piping bag fitted with a decorative tip, making sure the two bags are aligned by squeezing and twisting the large bag. Squeeze out a test pip to ensure the colors are coming out evenly.

Lay a large piece of plastic wrap on a flat surface. Spoon one color or flavor of your buttercream frosting in a log down the center. Repeat with the second color or flavor, spooning it parallel alongside the first color.

Fold the plastic wrap over to shape it into a two-toned log. Twist the excess plastic to seal the buttercream inside. Drop the plastic wrap log into a large pastry bag fitted with a decorative piping tip, using the excess plastic wrap to pull the log through the opening of the bag. Refrigerate for 10 minutes before frosting your cupcakes. Squeeze out a test pip to ensure the colors are coming out evenly.

In a large piping bag fitted with a decorative tip, use a spoon to scoop one color of frosting into one section of the bag, using your finger on the outside of the bag to help scrape it off. Repeat with your remaining color(s). Ensure you’re aligning the frosting so it starts at the same place in the bag. Squeeze the bag to slightly blur the colors together for a rainbow type effect. Twist the bag and frost your cupcakes. Squeeze out a test pip to ensure the colors are coming out evenly.