Place your thumb right below the edge of a knife, preferable a small paring knife. Use your non-cutting hand to grab the base of the tomato, and stabilize your hand against the cutting board. Place your knife’s tip slightly to the side of the core. Push your knife into the tomato about 1⁄4–1⁄2 inch (0. 64–1. 27 cm) deep. Cut out a small circle by twisting your knife. Pull up to remove the core.
Place your non-cutting hand on the left side of the tomato (if you are cutting with your right hand). Curl up your fingers into a claw shape and press your fingers tips lightly on the tomato. This type of grip helps to stabilize the tomato and prevent you from cutting yourself. Place the tip of the knife on the cutting board behind the rightmost side of the tomato. Keeping the knife tip on the cutting board, drag your knife straight down and through the tomato. A sharp knife will make cutting easier. Once you are through to the other side, lift up the knife. Reposition your knife at the top of the tomato, about 1⁄4–1⁄2 inch (0. 64–1. 27 cm) to the left of your last cut, depending on how thick you want your slices. Repeat the same dragging motion and continue across the tomato. Repeat for the second tomato half.
Depending on the make and model of your mandoline, you can dial-in or adjust your blade’s distance from the mandoline’s body to make thicker or thinner slices. Make sure your blades are sharp—this will help you make really thin slices without seizing up the machine or ripping the tomato.
Some models have spikes inside the holder to help secure slippery items like tomatoes. Mandoline blades can be very sharp and can slice neatly into exposed fingertips, so always use the hand-guard to protect yourself!
Start at the top of the mandoline body and slide the tomato and hand-guard down and over the blades. Try using a slight zig-zag motion to move over the blades; this will help to cut through the tomato’s skin and not squish it. Return to the top and drag down again to create another slice. Keep repeating this step until you reach the end of your tomato.
Hold the tomato slicer handle in your dominant cutting hand, with the sharp end of the blades facing the tomato. For extra leverage and stability, place your pointer finger on top of the handle where it intersects with the slicer’s frame. Use a sawing motion to work the slicer’s blades through the tomato. When you get about halfway through the tomato, move your non-cutting stabilizing hand to the top of the tomato so that it’s not in the way of the blades. You don’t want to cut yourself! Keep sawing back and forth through the tomato until you reach the cutting board.
