Tantalizing White Onion & Tuna Tart

Preheat oven to 425°F.

Cut fish into 1/2″ thick slices (if it’s not already). Sprinkle salt and fresh ground black pepper liberally all over the fish, and set aside.

Melt butter in a Dutch oven over medium heat. Add the onions and saute for a few minutes, until they become translucent. Be sure not to brown them in any way. Then reduce heat to very low, cover the Dutch oven tightly, and cook onions for about 20 minutes, stirring once or twice to prevent browning. Onions should be lightly yellow, but not brown, and most of the onion juices should be gone. If this state isn’t reached in 20 minutes, cover and cook longer, checking every 5 minutes for done-ness.

Whisk the eggs and cream together in a small bowl. Remove onions from heat, add egg and cream mixture and stir very thoroughly, until creamy and uniform. Season with salt and pepper to taste and add nutmeg. Finally, add the cheese and stir gently to distribute. Add paprika if desired.

Lightly sprinkle your work surface with flour. Roll out one sheet of puff pastry to slightly larger than the baking pan (I used a 10″ pie pan).

Line the baking pan with the layer of puff pastry, press it into the sides of the pan to form a pie shell. Pierce the shell all over with a fork. Fold half of the egg and onion mixture into the baking pan. Arrange the fish slices over it in a single layer, covering the entire surface of the pie. Fold the other half of the egg and onion mixture over the fish layer.

Lightly sprinkle your work surface with flour. Roll out the other sheet of puff pastry to slightly larger than the baking pan. If you wish to make patterns in the pie crust, make them at this time. I improvised and used a plastic cap of a water bottle to cut out incomplete circles in the crust. While baking, the circles puffed out and shrunk, creating little peek-a-boo openings in the pie.

Carefully transfer the top pie crust onto the top of the pie. Stretch out if necessary to distribute your patterns nicely. Using a rolling pin or your fingers, press the pie crusts together to the rim of the baking pan, thus cutting the extra crust off without stretching the crusts.

Bake for about 30 minutes at 425°F, or until the egg and onion mixture is set in the middle, and pie crust is golden and flaky.