Makes 2 cups
Preparation time: 75 minutes
- 2¼ lbs. plum tomatoes (about 6 to 8 large)
- 1½ cups distilled white vinegar
- 2½ tsp. coarse sea salt or kosher salt
- 1 cup sugar (or to taste)
- 1 tbs. grated onion or 1 tsp. onion powder
- ½ tsp. mustard powder
- ¼ tsp. ground cinnamon
- ¼ tsp. ground cloves
- ¼ tsp. ground allspice
- ¼ tsp. ground black pepper
Bring a large pot of water to a boil. Add the tomatoes and cook until the skins break and the flesh becomes soft, five to 10 minutes.
Drain the tomatoes and press through a fine-mesh food mill or sieve to remove the skins and seeds. Pour the sieved tomatoes into a medium-size saucepan. Add the vinegar and salt. Stir to combine.
Bring the tomato mixture to a boil and then whisk in the sugar, onion, and spices. Return to a low boil, stirring occasionally, and cook about one hour until the mixture has reduced to one-fourth the original amount and thickened. Some tomatoes are more watery than others, so additional cooking might be necessary to reduce moisture.
Your ketchup should be the consistency of tomato purée, slightly thinner than bottled ketchup; it will thicken when it cools. Pour into a sterilized jar. Cover and refrigerate for up to one month.
A food mill separates these skins and seeds from the pulp, while a food processor chops and purées everything together. The biggest difference is texture; with a food mill you get a refined, smooth sauce, while a food processor turns out a slightly aerated, granular sauce. When it comes to ketchups, barbecue sauces, and fruit butters, you are better off using the food mill or a fine sieve.