1. Process flour, almond powder, sugar, butter, and egg in a food processor for a few seconds until mixture becomes crumbly : do not process too much as the dough should be crumbly.
2. Transfer the dough onto a work surface. Gather it into a ball shape of dough with hands. Gently flatten the ball into a disk shape and wrap it in plastic wrap. Refrigerate it at least for 30 minutes.
3. To roll the dough: Put a plastic wrap covering on your work surface, place the dough on it. Then cover with another piece of plastic wrap. Let it sit for a few min to soften slightly. Roll the dough out into circle bigger than your tart mold. Then place gently into your tart mold (or ring). Using a sharp knife, trim the edges of the pastry to fit the tart pan. Prick bottom and side of tart thoroughly with a fork. Put it in the refrigerator or freezer until firm (about 30 minutes).
4. Preheat oven to 170C degree. Line the firm tart shell with parchment paper or aluminum foil and fill it with pie weights/dried beans.
5. Bake for 15 minutes and then remove the parchment and weights. Continue to bake for another 8 to 10 min at 180C degree or until the dough is just beginning to brown lightly. Cool on a wire rack until needed.
Make the filling
1. In a medium saucepan, add lemon zest, lemon juice, eggs, butter, sugar and sifted corn starch. Whisk to combine gently. Bring the mixture to a simmer over medium heat, whisking regularly to avoid lumps, about 7 to 10 minutes, until thickened.
2. Remove from heat, pour warm lemon filling into pie crust.
3. Put meringue powder and water in a large bowl and, using an electric mixer, beat until stiff peaks form. Then gradually add sugar, beating constantly until the meringue is thick and glossy.
4. Start to put the meringue around the edge of the filling (to avoid the meringue sink), then spread the rest to cover the whole lemon filling.
5. Bake for 5 to 10 minutes at 190C degree or until meringue is nicely golden.