Ingredients
Scale
- 3 tablespoons olive oil
- 2 medium white or yellow onions, thinly sliced
- 6 Roma tomatoes, skins removed
- ¾ cup granulated sugar
- 2 tablespoons apple cider vinegar
- 2 tablespoons lemon juice
- 1½ teaspoons kosher salt
- 1 teaspoon red pepper flakes
Instructions
- Heat olive oil in a large heavy-bottomed pot (like a Dutch oven) over medium heat. Add onions and caramelize, occasionally stirring with a wooden spoon, until intensely brown—about 17-20 minutes. Add 2 tablespoons of water and scrape to remove any caramelized bits at the bottom of the pot and mix.
- Add tomatoes and the remaining ingredients. Turn heat to medium-high and bring to a boil, stirring occasionally. Reduce heat to a simmer and continue to cook until tomatoes have broken down and become a jammy consistency, 60-75 minutes.
- Remove jam from the heat, let cool, and transfer to an airtight jar or container. Refrigerate for up to two weeks.