To Make Sweet Tart Pastry:.
In a food processor, place flour, almonds, sugar and salt. Blend for about 30 seconds to combine. Scatter in the butter cubes and pulse about 10 times until the largest pieces of butter are about the size of a pea. Pour in the egg yolk mixture and continue to pulse, about 3 seconds per pulse, JUST until the mixture no longer looks dry and small clumps begin to form.
Empty into a round 9 inch removable- bottom tart pan and begin to press the pastry into the tart shell with your fingers, evenly pressing it up the sides. You are aiming for about a 1/4 inch thickness.
Note: You will have more pastry than you need for this size of pan, so remove excess from the edge and freeze for future, or in my case I get out my individual tart shells and fill them to freeze for another time. Another option is to roll and cut with cookie cutters, sprinkle with sugar and bake along with the tart, later sandwiching them with jam.
Freeze for 30 minutes or overnight. Preheat oven to between 350F and 375°F Bake in the bottom third of the oven for 25 minutes until shell is golden brown. During the baking if the shell with puffs up in places, simply pierce it with a toothpick and it will deflate.
Remove from oven and patch any cracks with bits of the reserved dough, simply mashing it, gently into the hole, return to oven for pastry scraps to set. Set aside until filling is made.
To Make Filling:.
Rub together the lemon zest and sugar in a 2 liter saucepan until the oils have combined and the mixture looks slightly wet. Mix in the cornstarch. Add eggs and whisk together well. Whisk in juice and salt, place over medium heat and cook stirring constantly. As the mixture warms and starts to thicken a bit speed up your whisking, the faster you whisk the lighter the filling will become, which is the characteristic of this filling. Increase the heat if necessary, being sure to whisk constantly and vigorously.
Once the mixture coats the back of a spoon well it is done. Remove from the heat and whisk in the olive oil and butter quickly to cool mixture. Once completely mixed, pour into the cooled tart shell. Move the tart shell gently from side to side to get a nice level top, or pour in a concentric circle to form a slight decorative pattern in the filling. Refrigerate to set for about 1 hour. Will keep refrigerated for up to 3 days, if its around that long.