If you have tomatoes in your garden, or simply do not want to buy canned tomatoes throughout the winter, you can prepare your own conservated tomatoes. Below, I present a 100% natural recipe, no preservatives. To save the tomatoes, you have to cook and can them, similarly to making jam.
First, peel the tomatoes. The easiest way to do this is to make a small incision on their skin, and then put them in hot water for a minute. The skin wirl curl up, and it will be very easy to peel off. Then, you put your tomatoes in a huge bowl, and start to cook it. Simmer for a long time. During this, the tomatoes will get more soft, so you can easily mash them with a wooden fork. (depending on how big pieces of tomatoes you want to get). Allow it to simmer for about an hour, or even more. The more you cook them, the less water will your canned tomatoes contain. (It is better if they contain less, if you want to use the tomato sauce on pasta)
Meanwhile, prepare the jars, in which you are going to fill the sauce. Wash them very meticulosly, because any type of stain in the inside will make you tomatoes go wrong earlier. When they are clean, boil some water, and pour some hot water into the glasses, and close them. (When you pour the water, the jars might brake because of expansion. To avoid this, place them on a metallic surface, your sink will do). Roll around the jars, to let the hot water sterilize the whole inner side of them. Pour out the hot water. Once your tomatoes are ready, pour them into the jars right away. Fill the jars as high as possible, and close them. This way, the least possible amount of air will be locked in them. Do not worry, there will always be some air trapped. To best conservate the result, put the hot jars in thick layers of clothe, or anything, that will keep them from cooling down fast. I usually use my sleeping bag for this purpose. The best is if they stay warm as long as possible. About a day later, you can unwrap the jars and put it up you shelf proudly. Enjoy!
To add more flavour to the sauce, you can add whole garlic cloves, a little bit of sugar and salt, and at the end of cooking some olive oil and frsh basil leaves. This way, you can use the tomato sauce directly for pasta.