Martha and actor Alan Cumming make banana margaritas.
To sugar-rim the glasses, rub a lime wedge around rim of 2 stemmed goblets. Fill a saucer with sanding sugar. Dip goblet, upside down, into sugar.
Fill blender half full of ice cubes. Add lime juice, bananas, granulated sugar, and milk; blend. Taste for sweetness, adding more sugar, if desired. Blend a few seconds more; pour into sugar-rimmed glasses. Serve immediately.