The first of the true vine ripened tomatoes began to hit the farmers' market a couple of weeks ago. There have been locally grown hoop-house and greenhouse tomatoes for several weeks now...and these are good...but they are nothing compared to a tomato that has been allowed to ripen—while still attached to the vine—under the hot summer sun. From now until the crop begins to dwindle in the fall we will bring home as many as we think we can eat each week...red, yellow and orange cherry tomatoes, multicolored heirlooms and reliable jet stars. Most will be consumed raw—in salads or simply sliced, salted and drizzled with olive oil. Some will end up in a quick summer pasta, in a relish or on a BLT. A few will end up on a pizza, in a gratin or in a tart. Just this past week I put some of the first tomatoes of the season into a free-form tomato galette.
A free-form galette is another term for a crostata. The round of dough is placed on a parchment-lined baking sheet, the ingredients are layered in, and the edges are folded up and over the filling and pinched and pressed into place. In theory, nothing could be easier. But since tomatoes release abundant quantities of water as they bake, there are several things to consider when building the tart so you won't end up with a soggy, dough-y mess.
The first thing to do is salt the tomatoes. This is the same treatment that was given to the squash in my previous post. Slice the tomatoes and spread them on two or three layers of paper towels and sprinkle them evenly and lightly with salt—about as much as you would sprinkle on if you were "seasoning to taste" (since some of the salt will be absorbed, you are in fact also seasoning the tomatoes with this step). The salt will draw some of the water out of the tomatoes—almost immediately liquid will begin to bead on the surfaces of the tomatoes. After 15 to 20 minutes, blot up the liquid with more paper towels. As you blot, you will realize how necessary this step is. The paper towels will be saturated with all of the liquid that would otherwise have come out while the tart was in the oven.
When you layer the tomatoes into the tart, resist temptation to pile in too many. They should be just barely overlapping—just enough to get good coverage so that the visible surface of the tart is a solid layer of tomato slices. Even though a lot of moisture has been drawn off through the salting process, the tomatoes contain still more. This water needs to be able to evaporate as the tart cooks. If the tomatoes are piled on top of one another, the juices coming off of the tomatoes on the bottom layer have no way of escape. For a tart with a diameter of 10 inches, you will only need 1 1/4 to 1 1/2 pounds of tomatoes. I usually make up some of this weight (maybe 4 oz.) with cherry tomatoes. Halved and placed cut side up, the cherry tomatoes will contain their own juices within the little cups formed by their skins.
One other thing you can do to protect the crust from being saturated with tomato juices is to place something between the crust and the tomatoes...something that ideally will act as a barrier, protecting the crust from the liquid and at the same time absorbing some of that liquid. There are several ways to accomplish this. I have seen a couple of recipes that spread a generous layer of Dijon mustard over the raw crust. The mustard is allowed to dry a bit before the tomatoes are added. I haven't tried this particular method. It will certainly add complimentary flavor, but I would worry that some of the tomato juice might still get through. Other recipes add a layer of a good melting cheese (Susan Loomis uses Gruyère, Alice Waters uses Cantal). This is a very effective barrier. Some herbed goat cheese, or ricotta (mixed with a bit of flour and oil as in my Spinach & Spring Onion Tart) would also work well. Alice Waters adds a layer of wilted onions along with the cheese. Not only does this add great flavor (even more if herbs are added to the cooking onions...thyme, rosemary, or summer savory), it provides a layer that will absorb some of the tomato juices. It is this method that I used...a layer of a nice melting cheese on top of a layer of cooked onions. Some cooked leeks instead of the onions would be good too.
Finally, the tart should be baked on the lowest shelf of a hot oven. This will place it close to the heat source so the crust can start to set before the tomatoes begin to cook. If you have a baking or pizza stone, place the stone on the lowest rack (allow it to preheat for at least 20 to 30 minutes) and place the baking sheet with the tart directly on the stone. This will insure a cooked, well-browned crust. When you bake the tart, choose a rimless baking sheet or pizza pan so that you will be able to slide the tart off the pan and onto a wire rack immediately after removing it from the oven. If the tart is left to cool on the sheet pan, the crust will steam and become soggy.
This tart is best served slightly warm or tepid. Even if you want to serve it hot, it should definitely be allowed to sit for 15 or 20 minutes after it comes out of the oven (it can always be briefly reheated before serving). If cut into immediately, the still bubbling tomato juices contained within the crust will flow out all over the cutting board. If the tart sits for a few minutes, the juices will be reabsorbed by the tomatoes, onions and cheese. Not only will the tart slice more attractively if allowed to cool briefly, it will taste better too. And taste is really what this tart is all about...the intense, bright, summery flavor of vine-ripened tomatoes.
Provençal Tomato Tart
1 recipe Pâte Brisée (see below)
2 T. olive oil
2 medium yellow onions (about 12 oz.), halved and thinly sliced lengthwise
1 T. roughly chopped fresh thyme
Salt & freshly ground black pepper
1 1/4 to 1 1/2 lbs. vine ripened tomatoes (about 3 large)—multi-colored heirlooms, if you can get them. If you like, substitute a few cherry tomatoes for some of the weight of the vine ripes.
4 oz. Gruyère, coarsely grated
2 to 3 oz. goat cheese, crumbled or broken into large pieces
Roll out the dough: Allow the dough to sit at room temperature for a moment or two so it will be easier to roll out. Line a baking sheet with parchment paper; set aside. Roll out the dough on a lightly floured surface into a circle that is about 1/8-inch thick and is about 13 inches across. Trim any ragged edges. Brush off the excess flour. Transfer the dough to a parchment lined baking sheet. Cover loosely with plastic wrap and chill for at least 30 minutes.
While the dough rests, warm the olive oil in a sauté pan set over medium heat. Add the onions and the thyme, along with a generous pinch of salt, and cook until the onions are very tender—about 15 to 20 minutes. It's OK if they begin to caramelize, but it isn't necessary for them to do so. Set aside until they are completely cool (you don't want them to melt the butter in the crust). If you are in a hurry, place them in the refrigerator until they are cold.
While the onions cook, wash and core the tomatoes. Slice the tomatoes 1/4-inch thick and spread out on a double thickness of paper towel. If using any cherry tomatoes, halve them and arrange them cut side up on the towels with the vine ripes. Sprinkle the tomatoes evenly with salt and let them sit for about 20 minutes so they can give up some of their liquid. When you are ready to build the tart, blot the tomatoes with paper towels to absorb the excess liquid.
Spread the cooled onions in a circle in the center of the chilled pâte brisée, leaving a 1 1/2-inch border of dough. Scatter the Gruyère over the onions. Arrange the tomatoes on top of the Gruyère, overlapping them slightly. If using cherry tomatoes, arrange them attractively on top of the vine ripes. Arrange the goat cheese over the tomatoes. Pull up the edges of the crust and gently flip them over the filling to form a narrow, rustic edge. Pleat the dough as necessary, pressing lightly into place.
Set the tart on a baking stone positioned on the lowest rack of a preheated 400°. Bake until the tomatoes are bubbling, the cheese is browned and the bottom crust is crisp and browned—about 40 to 50 minutes. Immediately slide the tart off of the baking pan and onto a wire rack. Let rest for 15 to 20 minutes before serving.
Drizzle the tart with olive oil if desired. Tart serves 4 as an entrée, or 8 as an appetizer with a small salad.
Pâte Brisée (Short Crust Pastry):
1 1/3 c. all-purpose flour (150g)
1/2 t. salt
8 T. cold unsalted butter, cut into pieces (114g)
3 to 4 T. ice water
Combine the flour and the salt in a medium-sized bowl. Rub the butter into the flour until the butter is in small pea-sized pieces. Drizzle 3 T. ice water over the flour/butter mixture. Using your hands, fluff the mixture until it begins to clump, adding more water if necessary. Turn the dough out onto a counter and form into a mound. Using the heel of your hand, gradually push all of the dough away from you in short forward strokes, flattening out the lumps. Continue until all of the dough is flat. Using a bench scraper, scrape the dough off the counter, forming it into a single clump as you do. Form the finished dough into a thick disk. Chill for at least 30 minutes.