Prepare fresh pomegranate juice, if necessary.* Whisk together the vinegar, mustard and salt in a small bowl. Add the olive oil and pomegranate juice and whisk to combine; set aside.
Prepare fresh pomegranate arils, if necessary.** Shave fennel bulb very thin, preferably on a mandolin. Divide the arugula among the plates. Add grilled corn and thinly sliced fennel and top off with fresh arils and pepitas. Finish with some of the POM Vinaigrette and save some to pass at the table.
*To prepare fresh pomegranate juice, cut 2–3 large POM Wonderful Pomegranates in half and juice them with a citrus reamer or juicer. Pour the mixture through a cheesecloth-lined strainer or sieve. Set the juice aside.
**To prepare fresh pomegranates arils, score 1–2 large POM Wonderful Pomegranates and place in a bowl of water. Break open the pomegranates under water to free the arils (seed sacs). The arils will sink to the bottom of the bowl and the membrane will float to the top. Sieve and put the arils in a separate bowl. Reserve 3/4 cup of the arils from fruit and set aside. (Refrigerate or freeze remaining arils for another use.)