Wash, core, and quarter the tomatoes. Place them in a crockpot and cook on high heat for 3 to 4 hours. No need to add water, as the tomatoes will release their own juices as they cook.
Check the crockpot every hour and stir each time, until the tomatoes have released their juices. Then, add all the remaining ingredients.
Let the mixture cook for an additional 3 to 4 hours, checking the consistency and stirring periodically. The tomato juices should begin to evaporate, and the tomatoes should break down.
Once the juices are reduced and the tomatoes are fully cooked, transfer the mixture to a blender and blend until smooth.
Taste the blended mixture and adjust the spices or sweetener to your preference.
If the blended ketchup is too thin, transfer it to a pan on the stovetop and cook over low to medium heat until your favorite store-bought ketchup consistency is achieved. Stir occasionally to prevent burning.
Once the ketchup reaches your desired consistency, it's ready to be bottled and used.