1. To slice a tomato, use a paring knife to remove the stem and core (where the stem meets the top of the tomato). Be careful when removing the stem to remove as little of the tomato as possible. Only remove as much tomato as required to completely remove the stem and any green skin that surrounds the stem.
2. Place the tomato on a cutting board with the stem end towards your hand. Use a serrated knife to cut the tomato into slices of equal thickness.
3. To chop or dice a tomato, stack the tomato slices, and slice them into strips. If you want a very small dice of tomato, make the slices close together. If you want large chopped pieces, you probably only need to cut a few slices.
4. Turn the stack of tomatoes a quarter turn and slice the tomato into small pieces.
5. To slice a Roma or Plum tomato into round slices, place the tomato on the cutting board with the stem end on your right or left-hand side. Then cut the tomato into round slices, starting at the end opposite the stem end.