Adapted from Stir by Barbara Lynch
~from Savoring Time in the Kitchen
Serves 6 as a first course.
This makes six individual tarts, each about 4 inches across (feel free to make them in ramekins or even muffin tins). Or, you can make one 9 or 10-inch tart and cut slices from it.
Do ahead: The onions can be caramelized up to three days ahead. Keep them covered and refrigerated. The roasted tomatoes can also be made 2-3 days ahead and refrigerated. You can arrange the onions and tomatoes in the tart pan earlier in the day and then simply top with the already-cut crust right before baking.
What you'll need for the caramelized onions:
2 tablespoons olive oil
2 very large yellow onions, halved and thinly sliced
1 clove garlic, thinly sliced
2 teaspoons Dijon mustard
2 basil leaves, chopped
What you'll need for the roasted tomatoes (makes about 4 cups of roasted tomatoes)
3-1/2 pounds of plum or Roma tomatoes
4 cloves of garlic
6-8 springs of fresh thyme
1/2 cup of extra-virgin olive oil
Kosher salt and freshly ground black pepper to taste
What you'll need for final assembly and serving:
1 9 or 10-inch tart or pie pan or 6 small tart pans or ramekins
1 sheet of frozen puff pastry, thawed
Flour for your work surface
1 to 1 1/2 tablespoons honey
1 egg, beaten
3 tablespoons Mascarpone cheese or fresh ricotta for garnish
6 - 8 basil leaves for garnish (the number depends on how many individual servings you plan to make)
To make the caramelized onions:
Heat the 2 tablespoons of olive oil over medium heat in a large sauté pan. Add the onions and the garlic, reduce the heat to low, and cook, stirring occasionally, until the onions turn an even dark brown, 45 minutes to an hour. Don't rush the process! If you brown them too early they won’t get a sweet caramelized flavor and soft texture. If the pan dries out, add a tablespoon or two of water to the pan as needed. When the onions are nicely caramelized, take the pan off the heat and stir in the Dijon mustard and chopped basil. Season with 1/2 teaspoon of salt and some freshly ground pepper. Cool, the refrigerate until ready to use.
To make the roasted tomatoes:
To easily peel the tomatoes, cut a shallow X on the bottom (not stem end) of each tomato with a paring knife. Bring a medium saucepan of water to a boil and have ready a bowl of ice water. Boil the tomatoes, a few at a time, for 30 seconds or so and then remove with a slotted spoon and immediately plunge them in the ice water. This will will cause their skin to loosen and easier to peel. Using a paring knife to grab and peel the skin off of the tomatoes. Cut the peeled tomatoes into quarters lengthwise and seed them with your fingers, removing as much tomato juice as possible.
Heat the oven to 325°F. Divide the garlic slices between two large pyrex baking dishes or two baking sheets with sides, each about 9 x 13 inches or larger, spreading them out on the bottom. Place the tomato quarters in a large bowl and add the olive oil and toss with your fingers until coated. Lay the tomato pieces, inner side up in the pans. Sprinkle the salt over the tomatoes and season generously with black pepper. Bake until the tomatoes are soft and wrinkled but still retain their shape, 30-45 minutes.
Cool the tomatoes completely in the pan before transferring them to a storage container with a slotted spoon. Discard the thyme springs. Keep the roasted tomatoes refrigerated until ready to use.
To assemble and bake the tart(s):
Lightly flour a work surface, and roll the puff pastry out to 1/8-inch thickness. Invert a tart pan over the pastry sheet. With a sharp knife, cut out the shape you need by tracing around the pan with a paring knife. Repeat if using smaller tart pans or molds, adjusting to fit the sheet of pastry. Transfer the cut out dough to a very lightly floured sheet pan and refrigerate while you assemble the rest of the tart.
Heat the oven to 375°F. Use a finger to spread the honey on the bottom of the tart pan(s), dividing it among multiple pans, if using. Place a single layer of roasted tomatoes in the pan, overlapping as needed to cover the bottom completely. Distribute the caramelized onions over the tomatoes, dividing them evenly among multiple pans if using, and gently spread them to cover evenly.
Remove the cut dough from the refrigerator and place it directly over the onions. Lightly beat the egg and brush the top of the tart or tarts with the beaten egg. Sprinkle each with a pinch of additional kosher salt. Bake until the pastry is puffed and a deep, golden brown, about 20-30 minutes, depending on size.
If you want to fry some basil leaves for the garnish, heat the vegetable oil in a small saucepan until a basil leaf dipped into it sizzles. Place the remaining leaves in the oil and fry, turning them once, until crispy, 30 seconds to 1 minute. Drain on paper towel.
If you have made one large tart, slice it into six servings; (serve the tiny tarts whole).
Garnish each serving with a small dollop of Mascarpone cheese and a fresh basil leaf.