Wednesday, November 11, 2020

Slow-Roasted Tomato Jam #Recipe by Leslie Karst


Here in Santa Cruz, we’re lucky enough to still have the last tomatoes of the season on our vines. But with the cool weather now upon us, it was time to do my final harvest this last week. And boy, was it a harvest—my single Roma tomato plant bore some fifty pounds of fruit this year!

So what to do with all those glorious tomatoes? I decided to try my hand at a Slow-Roasted Tomato Jam—a sweet and savory condiment that goes perfectly on crackers with cheese, but would make for a luscious pasta sauce as well.

This recipe is for about five pounds of tomatoes, so if you use fewer (or more!), you can adjust the amounts of the other ingredients accordingly. And truly, the measurements are mere guidelines—feel free to alter them as your palate desires. 


Slow-Roasted Tomato Jam


¼ cup olive oil

1 med. onion

5 pounds tomatoes (Roma are best, but any will do)

1 teaspoon each, salt and black pepper

1 to 2 teaspoons sugar, to taste

2 tablespoons balsamic vinegar


Preheat oven to 300° F.

Line a large roasting pan with foil, and drizzle half the oil into it. 



Slice the onion thinly, then spread it out over the bottom of the pan. 

Cut the tomatoes into ½ to 1” chunks, and spread on top of the onions. Sprinkle the salt and pepper on top, then drizzle with the remaining oil.

Place in oven and roast, stirring every half hour or so, until the liquid evaporates and the tomatoes darken and become thick and gloppy. 


This could take anywhere from two to four hours, depending on the moisture content of your tomatoes. And you may want to crank the temperature of the oven up to about 400° F for the last half hour or so, to hasten the process. Just make sure to keep an eye on it, so the tomatoes don’t burn!

Once sufficiently cooked, taste the jam and add sugar as desired (1 to 2 teaspoons should be plenty). Finish by stirring in the balsamic vinegar. 


The tomato jam will keep refrigerated in glass jars for several weeks, or frozen in freezer bags for many months. 


🍅 🌿 🍝

The daughter of a law professor and a potter, Leslie Karst learned early, during family dinner conversations, the value of both careful analysis and the arts—ideal ingredients for a mystery story. Putting this early education to good use, she now writes the Lefty Award-nominated Sally Solari Mysteries, a culinary series set in Santa Cruz, California. 
An ex-lawyer like her sleuth, Leslie also has degrees in English literature and the culinary arts. She and her wife and their Jack Russell mix split their time between Santa Cruz and Hilo, Hawai‘i.

Leslie’s website
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WHAT A DEAL! For the entire month of November, Leslie's two Lefty Award-nominated books, MURDER FROM SCRATCH and DEATH AL FRESCO are Kindle Deals of the Month, on sale for only $1.99! Wow! 

Praise for Leslie's most recent Sally Solari mystery, the Lefty Award-nominated MURDER FROM SCRATCH:
“Karst seasons her writing with an accurate insider’s view of restaurant operation, as well as a tenderness in the way she treats family, death and Sally’s reactions to Evelyn’s blindness.”

Ellery Queen Magazine (featured pick)

All four Sally Solari Mysteries are available through Amazon, Barnes and Noble, and Bookshop.




  1. Yum! I made tomato jam a couple years ago, and am sold on it. My garden did not produce enough this year to make any, but I will definitely add it to my must-make list. And thank you, Leslie, for this recipe. I'll add it to my collection, too.

    It is very good on grilled cheese sandwiches in the winter. Elevates that simple sandwich to a whole new level.

    1. Oh, what a great idea, Karen! It's definitely going on my next grilled cheese! (I actually have a pair of socks with grilled cheese sandwiches on them, lol.)

  2. I’ll have to remember this for next year. Way past tomato season here.

    1. And it's now in the 40s in Santa Cruz, too. Brrrr! (Says the California native.)

  3. This does sound tasty, with multiple sues.
    I'm not having much luck growing tomatoes in south Florida. Critters attack the fruit and the latest plant has black spots.

    1. Yes, it's hard to grow tomatoes where it's humid. Good luck next year, Libby!

    2. I wonder what I meant to say in that first line above?!

  4. Thanks for the recipe, it sounds delicious! Our tomato season is over for this year, but I can't wait to try it next year.

  5. You're welcome, Kelly! And yes, definitely a recipe to file away for future tomato crops!

  6. I love this but like most of the others, our tomatoes are long gone. But I have high hopes for next fall and I will use your recipe then.

    1. Yes, we had a very late crop this year in California!