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1
Prepare the onions.
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2
Preheat the oven to 350F (175C).
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3
In a small bowl, toss together the onions, olive oil, rosemary, sage, thyme, and salt and pepper.
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4
Spread the mixture in a single layer on a baking sheet.
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5
Roast until the onions are soft and begin to color but still hold their shape, about 45 minutes.
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6
Remove the pan to a rack.
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7
Make the pastry.
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8
Place the flour and salt in the bowl of a food processor and pulse to combine.
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9
Add the butter and pulse until the mixture resembles coarse cornmeal, about 13 to 15 one-second pulses.
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10
With the machine running, add the ice water and process just until the dough starts to come together.
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11
Dont over-mix.
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12
Transfer the dough to a lightly floured work surface and form into a disc with your hands.
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13
Roll out the dough into a 13-inch circle, then ease it into a 10-inch tart pan, fitting it snugly against the sides and bottom, and trim the excess.
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14
Prick the bottom of the tart with a fork and refrigerate for 30 minutes.
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15
Make the filling.
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16
Whisk the ricotta, egg yolk, and olive oil in a small bowl until smooth.
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17
Stir in the creme fraiche and season with salt and pepper.
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18
Set aside.
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19
Make the royale.
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20
Whisk the egg, flour, and salt in a small bowl.
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21
Heat the cream and milk in a small saucepan until hot but not boiling, then slowly add it to the egg-flour mixture, whisking until smooth.
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22
Stir in the creme fraiche.
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23
Set aside.
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24
Bake the tart.
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25
Raise the oven temperature to 375F (190C).
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26
Place the rack on the bottom third of the oven.
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27
Spread the filling evenly in the tart shell.
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28
Scatter 3/4 of the onions in the tart shell and drizzle with the royale.
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29
Arrange the slices of cheese on top.
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30
Dot with the remaining onions.
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31
Bake the tart for 30 minutes, rotating 180 degrees after 15 minutes.
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32
Cover with aluminum foil and bake for 15 more minutes.
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33
For a deep golden brown crust, increase the heat to 400 degrees, leave the tart covered and bake for 10 to 15 more minutes.
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34
Cool on a rack.
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35
Serve warm.