In a saucepan on the stove, mix together all the ingredients until well combined. Bring mixture to a simmer over low/medium heat.
Once simmering, reduce the heat to low, semi-cover it and continue to cook for 20 minutes.
Once thick, take it off the stove and cool for 10 minutes before pouring into a container of choice. Now, place it in the fridge to chill for at least a few hours before using.
Store ketchup in the fridge in an airtight container for at least 4 weeks.
