Combine all the ingredients in a medium saucepan over medium heat; whisk until smooth.
When it comes to a boil, reduce heat to low and simmer for 20 minutes, stirring often.
Remove from heat and cover until cool.
Chill and store refrigerated in a covered jar or container.
Notes
Ketchup will last for at least seven days in the refrigerator. *Some people found this too sweet. You can start will a little less if you prefer, then add more to your taste.