There is a widespread belief that canned fruits and vegetables like diced tomatoes cannot substitute for or compare to the quality of fresh produce. There are benefits and drawbacks associated with both fresh and canned food. When it comes to tomatoes, you can get ones that are still fresh throughout the entire year. Tomatoes have the best flavor when they are fresh from the vine, which happens to be approximately half the year. Because tomatoes are picked when they are typically at their peak of ripeness, diced canned tomatoes may be a more flavorful option when purchased during the other half of the year. 
Canned tomatoes are not only a more cost-effective and convenient option, but they also have a longer shelf life, which means that even if you forget about them, they won't go bad. The United States Department of Agriculture (USDA) reports that canned tomatoes are the most popular type of canned vegetable in the country. You might prefer using canned tomatoes rather than fresh ones depending on the time of year and the recipe you're making. Here is how you can use fresh tomatoes instead of canned tomatoes so that you can always use the type of tomatoes that you prefer or that you already have on hand. How to Use Fresh Tomatoes in Place of Diced Canned Tomatoes in a Recipe There are numerous varieties of fresh tomatoes, some of which are heirlooms, while others are hybrids. Heirloom tomatoes such as Black Krim and Brandywine may only be available during certain times of the year in grocery stores, but grape, Roma (plum), and cherry tomatoes are typically available year-round. According to Julia Chebotar, a chef based in New York City and the winner of this season's Chopped! competition, "You can usually substitute two cups of fresh chopped tomatoes for one 14.5-ounce can of diced tomatoes." 
"When following a recipe that calls for whole canned tomatoes, you can use fresh tomatoes that have been peeled and left whole in their place. If a recipe calls for canned tomato puree, fresh tomatoes that have been cooked down and pureed on their own can stand in for the canned variety." Chebotar recommends the following steps be taken to use fresh tomatoes rather than canned tomatoes: What You Will Need
- tomatoes
- coring tool
- knife for paring
- pot
- 2 bowls
- cold water
- cutting surface
- colander
- Give Raw Tomatoes a Good Rinse
You should wash your hands for twenty seconds in water that is warm and soapy. After that, pass the tomatoes under a steady stream of lukewarm water for a few minutes.
- Bring to a boil and then peel
To make peeling the tomatoes more manageable, blanch them in hot water. First, cut an "X" into the bottom of each tomato with a paring knife, then remove the core from the tomato at the stem end. 
After blanching the tomatoes in boiling water for 30 to 60 seconds at a time, remove them one at a time and place them in a dish containing ice water. The tomato skins are quite easy to remove once the tomatoes have had time to cool down.
- Prepare the Tomatoes for Eating
After cutting the tomatoes in half lengthwise, give each half a gentle squeeze to remove the majority of the seeds and watery pulp. Use your finger or a small spoon to remove any remaining seeds or pulp that remains. If the juice of the tomatoes is required for the dish, strain the pulp of the tomatoes through a strainer set over a bowl while reserving the liquid.
- Cut the Tomatoes Into Dice
Put the tomatoes on a cutting board, then dice them into pieces that are either 1/4 inch or 1/2 inch in size, depending on your preference. After that, put them to use in the manner specified in the recipe. You are welcome to freeze any leftovers. Tip Raw tomato consumption works very well with fresh tomatoes. You may dice them up and use them as a topping for salads and sandwiches, or you can eat them on your own as a snack. 
You can also cook fresh tomatoes for making homemade marinara sauce, pizza sauce, or any other sauce that uses tomatoes as the primary ingredient. How to Make a Tomato Sauce Using Canned Tomatoes Instead of Fresh Tomatoes: Tomatoes are typically sold in cans of either 14.5 or 28 ounces and are available in a wide variety of preparations, such as peeled, whole, diced, crushed, fire-roasted, chopped, etc. Even though fresh tomatoes are packed with flavor and nutrients while they are in season, they are likely to be tasteless and tough for the better part of the year. Because they are typically selected and processed at the pinnacle of their ripeness, the quality of canned tomatoes is significantly more consistent. Canned tomatoes are a handy alternative to fresh tomatoes that are not currently in season or that you do not already have on hand. When using canned tomatoes as a substitute for fresh tomatoes, Chebotar recommends choosing whole, peeled tomatoes whenever possible. He continues by saying, "They tend to be higher quality, though canned diced tomatoes can also work when you're in a pinch." But diced canned tomatoes can also be used in a pinch. The amount of whole peeled tomatoes that are equivalent to one 28-ounce can of tomatoes or two 14.5-ounce cans of tomatoes is approximately 10 to 12. Many different types of soups, stews, chilies, curries, and sauces all benefit from the inclusion of diced canned tomatoes. Foods like pasta, pizza, enchiladas, chili, and sloppy joes can all benefit from the addition of canned tomato sauce. 
The United States Department of Agriculture advises that home-canned tomatoes be consumed within a year of being processed. Tomatoes purchased in a store usually have a shelf life of about 18 months. Tip When looking for canned tomatoes, the National Library of Medicine in the United States suggests selecting brands that do not have any added salt. Cooking with Frozen Tomatoes: A Guide to Making Sauce:
- Start by peeling the Tomatoes.
To thaw the skin of a frozen tomato, place it under warm running water for twenty to thirty seconds while holding it. To peel the tomato, pull the skin that has become loose from the fruit, and then throw it away. Proceed in this manner for a total of four to six large tomatoes, or eight to ten medium-sized tomatoes.
- Make a Sauce from the Tomatoes
Put the tomatoes that have been peeled into a bowl so that they can thaw until they are pliable enough to be crushed. To break the tomatoes down into small pieces, mash them with a fork or squeeze them by hand using your hands.
- Prepare the tomato sauce by cooking it.
Cook one medium sliced onion and three to four minced garlic cloves (depending on your taste preferences) in a large pot over medium heat while stirring until the vegetables are a light golden brown color. Add 2 to 3 tablespoons of olive oil to the pot as well. 
Put the crushed tomatoes in the pan and add two to three tablespoons' worth of finely chopped fresh herbs like basil, thyme, marjoram, and oregano. oregano. Add a pinch or two of freshly ground black pepper and a little bit of salt to the mixture and season it lightly with salt.
- Stir and Simmer
Keep stirring the mixture consistently until it reaches a boil. Turn the heat down to medium and let the sauce boil uncovered for one hour to create a chunky sauce that may be served over pasta. Continue to simmer the sauce for a further half an hour to an hour until it reaches the desired consistency. This will result in a smoother sauce.
- Allow It to Chill and Puree It
After the mixture has had time to cool, put it in a blender and puree it. Tip While the sauce is cooking, a very small amount of salt should be added to tomato-based sauces. This is because the flavors become more concentrated as the sauce dries out and becomes thicker.