1/2cupunsalted butter (1 stick) cold and cut into 1-inch pieces
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1large egg
1tablespoonwater
=====mustard coulis=====
1medium-sizedred onion
1 1/2poundscherry tomatoessimilar in size
2tablespoonsextra-virgin olive oil
3/4teaspoondried oregano
1/4teaspoonKosher salt
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1tablespoonDijon mustard
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1/4teaspoondried oregano
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olive oil for brushing
Maldon sea salt
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fresh lemon zest
basil
Instructions
=====crust=====
Put the flour, sugar, salt, and butter in the bowl of a food processor fitted with a metal blade. Pulse until the mixture becomes coarse crumbs.
Add the egg and water and pulse to incorporate and then mix on low to form a dough. Form the dough into a 1-inch high disk with your hands and place on a sheet of parchment paper on your work surface. Cover with another sheet of parchment and roll to an 11-inch round. Chill the round for 5 minutes in the refrigerator.
Remove the dough from the refrigerator, peel off the parchment paper, and place in a 9.5-inch tart pan with a removable bottom. Trim the excess by rolling a rolling pin over the top. Save the excess dough for patches, if necessary. Prick the bottom of the tart with a fork - all over. Freeze for 20 minutes or until ready to use.
Preheat the oven to 375ºF. Place the lined tart on a rimmed baking sheet. Put a sheet of parchment in the pan and fill with pie weights. Bake for 20 minutes. Remove the weights. Bake for 5 more minutes for a total of 25 minutes. Cool the crust completely.
=====mustard coulis =====
Preheat oven to 450ºF. Slice the onion and toss it in a bowl with a half pound of the cherry tomatoes and olive oil. Put on a baking sheet and sprinkle with 3/4 teaspoon of oregano and Kosher salt. Roast at 450ºF until the tomatoes start to brown, about 15 minutes. Cool slightly and blend in a blender with the Dijon mustard. Taste and adjust salt, if necessary. Decrease the oven heat to 425ºF.
Half the remaining tomatoes crosswise. Spread the mustard coulis onto the dough. Sprinkle with 1/4 teaspoon of oregano. Arrange the tomatoes on top of the filling tightly in concentric circles overlapping slightly. Start on the outside and work towards the center. Brush the tomatoes with olive oil and sprinkle with Maldon sea salt. (You may have some extra filling and tomatoes depending on how you build your tart.
Bake the tart for 25 to 30 minutes, until the crust is golden brown and the tomatoes are beginning to char.
Cool the tart for at least 10 minutes. Serve warm sprinkled with lemon zest and shredded basil leaves.