This caramelized onion tomato jam is easy to make with only a handful of ingredients. It’s a wonderful accompaniment to a cheese plate, charcuterie board, or even as a spread for sandwiches!
This post was originally published in 2018 and updated in 2021 with new photos and improved instructions.
This caramelized onion and tomato jam is simple to prepare and incredibly versatile. The key is patience: cook the onions low and slow until they turn a deep golden brown and develop a natural sweetness. Once the onions are deeply caramelized, add balsamic vinegar, diced tomatoes, and sugar, then simmer until the tomatoes break down and the mixture thickens into a glossy, jam-like consistency.
The finished jam is sweet, tangy, and savory all at once. It pairs beautifully with a cheese board or charcuterie, works as a sandwich spread or grilled cheese addition, and complements potato dishes and eggs. It also makes an elegant crostini topping when paired with soft cheese or whipped cream cheese.
Recipe ingredients
Ingredient notes
- Tomatoes: Vine-ripened or plum tomatoes work well. I haven’t tested grape or cherry tomatoes for this recipe, so those may change the final texture.
- Onion: Sweet onions like Vidalia are my first choice, and red onions give the jam a deeper color. Yellow or white onions are fine too.
Step by step photos
1. Heat oil in a pan and add thinly sliced onions with half the salt. Spread the onions in an even layer and cook over low heat, stirring occasionally, until they reach a deep golden brown, about 40–45 minutes.
2. While the onions caramelize, prepare the tomatoes. Remove the stem and scoop out the seeds before dicing.
3. Add the tomatoes, remaining salt, sugar, and balsamic vinegar to the pan with the caramelized onions. Increase the heat slightly and simmer, stirring occasionally, until most of the liquid has evaporated and the mixture thickens into a jam-like consistency.
Tips and tricks
- I keep tomato skins on since the jam is chunky and they blend into the texture, but you can peel them if you prefer a smoother result.
- Adjust the sugar, vinegar, and salt to your taste. Tomatoes vary in sweetness, so start with less sugar and add more during cooking if needed. A splash more vinegar at the end brightens the flavor.
- If tomatoes aren’t super ripe, that’s okay—the long cooking time and added sugar balance and concentrate the flavors.
Recipe FAQs
Store leftovers in an airtight container in the refrigerator for up to one week.
Yes. Freeze in an airtight container for 3–4 months. Thaw in the refrigerator before serving; texture and flavor hold up well.
Serve it with home fries, eggs, grilled cheese, or as a condiment on sandwiches and burgers. It’s also excellent on crostini with soft cheese or as part of a cheese or charcuterie board.
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📖 Recipe
Caramelized Onion and Tomato Jam
This caramelized onion and tomato jam is an ideal companion for cheese plates, potatoes, and sandwiches. Balsamic vinegar adds a bright note that balances the sweet onions and tomatoes.
- Author: Kate
- Prep Time: 10 minutes
- Cook Time: 1 hour 15 minutes
- Total Time: 1 hour 25 minutes
- Yield: 2 cups
- Category: Sides
- Method: stove top
- Cuisine: American
Ingredients
- 1 tablespoon olive oil
- 1 large onion or 2 small onions, thinly sliced
- 1 teaspoon salt, divided
- 2 pounds tomatoes (about 6–7 medium vine tomatoes)
- 3 tablespoons granulated sugar, or to taste
- 3 tablespoons balsamic vinegar
Instructions
- Heat olive oil in a large skillet over low heat.
- Add thinly sliced onions and sprinkle with about ½ teaspoon salt.
- Spread the onions in an even layer and cook until deep golden brown, about 40–45 minutes, stirring occasionally.
- While the onions cook, remove stems from the tomatoes, halve them, scoop out seeds and pulp, and dice the flesh.
- When onions are caramelized, increase heat to medium-low and add the tomatoes, balsamic vinegar, sugar, and the remaining ½ teaspoon salt. Scrape any browned bits from the pan.
- Cook, stirring occasionally, until the tomatoes break down and the mixture thickens, about 30 minutes. Lower the heat as needed to prevent burning.
- Taste and adjust salt, sugar, or vinegar. If you add more vinegar or sugar, cook another minute or two to incorporate.
- Serve immediately or store in a sealed container in the refrigerator for up to one week.
Notes
- Sweet onions are preferred, but any onion will work. Red onions deepen the jam’s color.
- Three tablespoons of sugar gives a balanced sweetness. Start with 1–2 tablespoons if you prefer less sweetness and adjust while cooking.
- After the onions reach deep golden brown, you can continue to cook them longer on low for more caramelization.
- The jam freezes well in an airtight container for 3–4 months.