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1
For the dough: In a food processor, pulse to combine the flour and salt.
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2
Add the butter and pulse 3 to 4 times, then drizzle in the ice water and pulse until the dough holds together easily when squeezed with your fingers.
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3
Add more ice water, 1 teaspoon at a time, if needed.
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4
Divide the dough in half, pat each portion into a round disk, wrap with plastic wrap and chill in the refrigerator for at least 30 minutes.
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5
For the salad: In a small jar with a tight-fitting lid, combine the oil, vinegar, mustard, parsley, tarragon, sugar, shallots and some salt and pepper.
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6
Shake to mix the dressing and chill until ready to use.
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7
Place the greens in a large bowl, drizzle about 1/4 cup dressing over and toss to combine.
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8
For the tart: Preheat the oven to 375 degrees F. Line a baking sheet with parchment paper.
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9
Toss the tomatoes with the oil, onions and some salt and pepper, then set aside.
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10
On a lightly floured surface, roll one disk of the dough into a 12-inch round, about 1/8-inch thick.
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11
Transfer to the prepared baking sheet, then fold and crimp the edges.
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12
Spoon the sour cream and mustard evenly on the dough.
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13
Top with the tomato mixture and the goat cheese.
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14
Make an egg wash by beating the egg with 1 teaspoon water.
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15
Brush the egg wash around the tart edges.
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16
Transfer the tart to the oven and bake until the crust is golden and the tomatoes soften, about 45 minutes.
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17
Cut into squares to serve with the salad.
