First things first, before cutting your tomatoes, give them a quick wash under cold running water, and make sure you’ve removed any produce stickers before you begin cutting. (We’ve all forgotten to do this at least once… maybe twice.) Though you’re probably used to using a chef or santoku knife to dice vegetables with, since tomatoes have a thin, slippery peel, the best thing to use is a serrated knife, which will easily saw through the peel without crushing the flesh. Some varieties of tomatoes can be ultra-juicy, so if you can, use a cutting board with notched reservoirs that can catch extra liquid.
How to Dice Tomatoes
- Use the tip of your knife to cut out the small bit where the tomato was attached to the stem, then cut the tomato in half. Gently squeeze out the seeds into the sink, or directly into your trash can/compost bin. Run a clean finger through the tomato’s inside chambers to remove any stubborn seeds and watery, jelly-like pulp, then put the halves cut-side down on the cutting board.
- Holding your knife parallel to the cutting board, cut slices from the tomato that are as thick as you’d like your dice to be.
- Lay the slices onto the cutting board, stacking if you wish, then cut into strips the same width as you cut your slices. Finally, cut those strips crosswise into the size you prefer.
- Cut a thin slice from the bottom to create a flat surface on which to stand the tomato. Cut wide strips from the top, curving down to the bottom, to separate the flesh from the inner seed core. Cut all the flesh away in this manner, leaving the seedy core of the tomato; discard the core. Cut each strip of flesh lengthwise as wide as you want your dice to be, and then cut these strips crosswise into dice.
When to Use Diced Tomatoes
Diced tomatoes are best when used immediately, so try not to cut them too far ahead of when you'll be needing them. If you must dice ahead of time, put them in a sealable container with a small piece of paper towel to absorb excess moisture, then refrigerate. Even though you should never store tomatoes in the fridge (it destroys some of their flavor compounds and makes their texture unpleasantly mealy), once tomatoes are cut, they must be kept cold to prevent spoilage. Once diced and refrigerated, use your tomatoes within a day; if you need to keep them longer, mix with enough olive oil to cover completely.