Use a sharp knife to cut the ingredients into pieces. Cut the onion into small, finger-sized pieces. Divide the tomatoes into similarly sized chunks too. You can cut them into wedges a little larger than the onions. These peppers are so hot that they will irritate your skin. Always wear kitchen gloves when handling them. Slice off the stems, then cut the peppers from side to side. Divide them into slices a little bigger than the onions. You don't have to remove the seeds. Be careful of any lingering pepper juice. Wash it off when get the chance. Avoid touching your eyes. Place a pan on the stove and add the oil to it. Olive oil is a common choice, but other cooking oils may be used instead. Turn on the stove to let the pan heat until the oil is hot. When the oil is hot, it glistens. It flows smoothly if you tip the pan. It should not smoke, so if you see smoke, move the pan off the heat. Canola oil is a standard replacement for olive oil. It has less flavor. Other vegetable oils, including corn oil or peanut oil, may also be used. Add the 3 ingredients you cut earlier, stirring them with a spoon to coat them in oil. The heat softens the ingredients and begins drawing out their flavor. Measure out the liquids and pour them into the pot. Also add the salt to season the sauce. Reduce the heat to a medium-low setting. The sauce should gently bubble, indicating that you have it at the right temperature. Leave the pot on the stove, uncovered, for 20 minutes. After the 20 minutes are up, remove the pan from the heat. For safety, let the sauce sit on the stove for about 5 minutes. The open your food processor and pour the ingredients into it. Turn on the processor to break down the ingredients into a smooth sauce. Use resealable hot sauce bottles or mason jars to hold the sauce. Make sure the jars have been thoroughly washed and disinfected. Pour the sauce into a funnel placed on top of the bottles, then let the bottles cool, uncovered, on the counter. After 10 to 20 minutes, when the bottles no longer feel hot to the touch, move them to the refrigerator. Homemade hot sauce can stay fresh up to 6 months and sometimes longer than that.

Summary:
Slice up the onion and tomatoes. Cut apart the peppers. Heat oil in a pan over medium-high heat. Cook the onions, tomatoes, and peppers into the pan for 10 minutes. Add vinegar, salt, and water to the pan. Reduce the heat so the sauce simmers for 20 minutes. Cool the sauce for a few minutes and pour it into a food processor. Pour the sauce through a funnel into resealable containers. Refrigerate the sauce in the resealable containers.