Inspired from: Tarte au thon
Comment: Preferably use a pie plate with high edges, like for quiche.
A good technique to precook the dough is to put the dough in the mold, then make holes in the bottom with a fork as normal, arrange a parchment paper in the pie and fill it with dry beans, which you can recover once the dough is cooked. I use here 2 eggs for the filling, but if your mold is really high-rimmed (> 2.5 cm), use 3 eggs, 2 dl cream and 2 dl of milk and maybe a little more tuna. Do not forget to butter the mold or (which is unsightly) to dispose a sheet of parchment paper under the dough.
1 precooked dough (180C 25 min convection heat) in a pie plate with a high edge.
1.5 dl milk
1.5 dl cream
~300 + g tuna drained (~400 g before)
1 tablespoon slightly rounded cornstarch (Maïzena)
S + P
Prepare the filling: beat together the eggs, the milk, the cream, some gratings of nutmeg (1/2 walnut), cornstarch, salt and pepper, set aside.
Slice the onion finely in strips then sweat with a little EVOO and salt in a pan. Reserve.
Peel (opt) the tomatoes, then cut them to have 8 nice slices (~ 4 mm thick).
Seed the rest and cut into small cubes.
In the precooked dough, spread finely ~1 tablespoon grain mustard (old style mustard).
Then spread over the onions, then the tomato dice on the onions.
Spread the crumbled tuna over, and pour the filling. Arrange the 8 slices of tomatoes on top, around the edges, and bake at 220C for 30 to 35 minutes.
Serve with a green salad.