How to Make It
Using a damp cloth, wipe down a large work surface. Stretch a 14-by-24-inch sheet of plastic wrap over the surface and use the damp cloth to smooth it out. Sift a generous layer of cornstarch over the plastic wrap.
In a large microwave-safe bowl, mix the rice flour with the sugar, pomegranate juice, lime juice and salt until smooth. Cover the bowl tightly with plastic wrap. Microwave for 2 minutes, until the batter starts to thicken at the edges. Remove the plastic and, using a rubber spatula, stir the mixture until mostly smooth; a few small lumps are OK. Re-cover the bowl with the plastic and microwave for another 2 minutes, until the mixture is stiff and sticky. Using a rubber spatula, stir quickly and vigorously until smooth, about 30 seconds.
Working quickly, scrape the mixture onto the prepared work surface and lightly sift with cornstarch. Using a rolling pin dusted with cornstarch, roll the mixture into an 8-by-10-inch rectangle, about 1/4 inch thick. Let stand at room temperature until cool to the touch, about 15 minutes. Using the plastic wrap, transfer the mixture to a rimmed baking sheet; fold the plastic wrap over to cover completely. Refrigerate until firm, about 45 minutes.
Dust another rimmed baking sheet with cornstarch. Dip a 3/4-inch round cutter in cornstarch and stamp out rounds. Transfer the mochi to the prepared baking sheet. Refrigerate, uncovered, until ready to serve.
Sweet glutinous rice flour, aka mochiko flour, is available at Asian groceries.