For the cupcakes pictured, I used a Wilton 104 petal tip and a two-tone technique. I used a pomegranate aril in the center but you could also use cake sprinkles or decorating balls (dragees).
I found several helpful tutorials for piping the cupcakes. This Two-Tone Buttercream Rose Cupcake Tutorial was great in explaining how to fill the decorating bag to achieve the color tinged petals. For the flower technique itself, I followed this Buttercream Flower Cupcake Tutorial. I used the fourth technique that was demonstrated.