Tips: Be sure to use a nonreactive bowl--stainless-steel, enamel-coated or glass--when working with acidic food like grapefruit. Reactive vessels, such as aluminum and cast-iron, can impart off colors and/or flavors. To suprême: Use this technique to get pretty, pith-free citrus sections every time. Cut a thin slice off the top and bottom of the fruit with a large sharp knife. Place on a cutting board. Remove the peel and white pith below, following the curve of the fruit as you go. Working over a bowl, switch to a small sharp knife and cut each segment from the surrounding membranes. Squeeze any extra juice from the membranes, if desired.