In the last few weeks I have been making many batches of slow-roasted tomatoes. These are tomatoes — typically Roma, San Marzano, or another sauce-friendly tomato — that have been sliced, tossed with olive oil, salt and pepper, and then roasted on a cookie sheet at 250 to 300 F for several hours. The slow cooking concentrates the flavors, creating a supercharged tomato experience. Consequently, the roasted tomatoes are best used as accents, as a topping for free-form lasagna, in macaroni and cheese, or as part of a sandwich. The ones I don’t eat I put into the freezer.

But it takes a lot of fossil energy to slow roast tomatoes, and so I have been trying to use my solar oven.

Drying fruits and vegetables in a box-type solar cooker like mine is tricky because the oven works best when the cooking chamber is sealed. Drying something, however, requires a constant flow of dry air; otherwise, you’re creating tropical rain forest-like conditions, where nothing ever dries out. There are special solar dryers that address this problem, which I might look into next spring. But in the meantime, adding a few kitchen items to my oven made my drying project a reasonable success.

The diagram below shows how I did it. The Roma tomatoes (sliced in half and heavily salted to draw out the moisture) are placed on a wire rack, which goes on a cookie sheet, which goes on an upside-down bowl. This stacking gets the tomatoes close to the glass, and increases the level of solar energy. To allow air exchange, I placed rolled up towels under two corners of the lid. This created a path for air to enter and exit the box without losing too much heat.

Since it was October, the day was fairly short and the sun was low in the sky, so the result of this experiment was half-roasted tomatoes. Fortunately, I was baking pizza that night, so I put the tray of tomatoes into the oven after I turned it off — the heat retained by the oven and the baking stones was enough to finish the roasting.

Next summer, I think I’ll start my solar drying experiments in June…

Random link from the archive: Smoked Eggplant

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