For the sour cherry ketchup, rinse the sour cherries with cold water and drain. Remove the stones – it is best to use a cherry pitter.
Peel and finely dice the onions. Peel and finely chop the ginger root. Heat the oil in a pot and sauté the onions until translucent. Add the ginger and sauté briefly. Deglaze with the vinegar and add the remaining ingredients (except the alcohol) to the pot.
Bring to a boil. Reduce heat and simmer over medium heat for 30 minutes. Meanwhile, stir frequently.
Remove the cardamom pods and puree the sour cherry mixture with a hand blender to a fine puree. If necessary, pass through a hair sieve. Bring to the boil again and simmer for a few minutes until the ketchup has reached the desired consistency.
While still hot, pour the sour cherry ketchup into carefully cleaned, sterilized bottles. Drizzle a few drops of alcohol over the top, light and seal tightly.