Slow Roasted Tomato Sauce

Tomatoes are cut in half and placed cut-side down on a baking sheet to slow-roast them.
Tomatoes are cut in half and placed cut-side down on a baking sheet to slow-roast them.

Last year I did a Standard-Examiner column and a blog post on how easy it is to make slow-roasted tomato sauce. Now that my tomatoes are getting ripe in the garden, I decided to post the directions again. It will save you a lot of effort and mess if you want thick, rich tomato sauce from fresh tomatoes.

Since tomatoes contain a lot of liquid, homemade sauces usually require hours of stovetop simmering to thicken. But if you roast them in the oven at a low, slow temperature —  around 200-225 degrees — it removes most of moisture. Several pounds of tomatoes can be condensed down into a few cups of sauce that be frozen for later use. I like to use it in my spaghetti sauce and Garden Tomato Bisque.

You don’t have to do any peeling. After you take them out of the oven,  you just pinch the skins and they slip right off.

Roasting caramelizes the tomatoes’ natural sugars, giving them a deep, rich sweetness.

The only drawback to slow-roasting is that it ties up your kitchen for a long period of time — about six to eight hours. And, it adds some heat to your kitchen, although the temperature is low.

Because of this, I often let my tomatoes roast during the night, and wake up thinking I’m in an Italian restaurant.

37. GARDEN TOMATO BISQUEFor me, it’s preferable to home canning tomatoes. USDA guidelines state that quart jars of tomato products should be processed in a boiling water bath for 95 minutes, for Wasatch Front altitudes.  That’s a lot of hot water sloshing around on your stove and steaming up your kitchen.

Don’t get impatient and turn up the heat. I tried roasting a batch of tomatoes at 350 degrees. After an hour, the skins were charred and the tomatoes had a burnt flavor. The kitchen also reeked.

The following recipe uses plum tomatoes. The round, slicing-style tomatoes are usually larger and more watery, so add a little more roasting time. If your plum (or roma) tomatoes are small, use lower heat or less roasting time.


About 20-25 medium or large plum tomatoes

1 tablespoon olive oil

Italian seasoning (dried basil, rosemary, oregano), optional

About 1/2 teaspoon salt

1. Spread the olive oil on a large baking sheet or pizza stone. Sprinkle it with the herbs, if using, and salt. You can also use a silicone baking mat (Silpat).

2. Cut off the stems of the tomatoes and cut each tomato in half lengthwise.

3. Place the tomatoes cut-side down on the pan. It’s OK if they touch; they will shrink during cooking.

4. Turn the oven to 200 degrees. Place the tomatoes in the oven and let them roast for 6-8 hours.

5. Check occasionally to make sure they’re not burning. You can turn down the temperature as low as 170 if you need to let the tomatoes roast longer.

6. The tomatoes should look shriveled and dark red, but still pliable. Turn off the oven and let them cool for a half hour or more.

Pinch the skins; they should lift off.  Place the tomatoes in a blender or food processor and puree. You can leave the sauce a little chunky if desired.

You may want to strain the sauce through a sieve to remove seeds, but I think the seeds are the proud badge of a homemade sauce.

This recipe makes about 2 to 3 cups of very thick tomato sauce, but not quite as thick as tomato paste. You can freeze it, or use it immediately on pasta, pizza and any other way that you would use tomato sauce.

Click here for my Garden Tomato Bisque recipe.

Here are two other bloggers that have featured Slow-Roasted Tomatoes.

Kalyn’s Kitchen 

Apron Strings


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