To prepare the tartlet shells, preheat the oven to 375°F (190°C). Line 2 baking sheets with parchment paper, or silicone mat.
Cut each puff pastry sheet into 6 rectangles. Arrange them on prepared baking sheets.
Using a sharp knife, score the pastry about ¼ inch from the edges to create a border. Be careful not to cut all the way through.
Brush on cream over the edges.
Bake for about 15 minutes, or until the crusts are puffed and golden.
Cool completely on wire racks. Once cooled, flatten the inside of puff pastry with a fork to make room for filling.
Meanwhile, make the lemon curd filling. In a medium saucepan, mix together water, lemon juice, sugar, cornstarch, flour, lemon zest and salt. Bring the mixture to a boil over medium heat, stirring constantly.
In a medium bowl, whisk egg yolks lightly. And then temper the yolks by adding about half cup of hot lemon juice mixture into the egg yolks and stirring vigorously.
Return the egg mixture back to the saucepan. Continue cooking for 3-5 minutes, continuously stirring.
Stir in butter. Remove from heat and cool slightly. Transfer the lemon curd filling into a pastry bag, or a ziploc bag with one corner cut. (I find it’s easier to pipe the filling, as it thickens quickly as it cools.)
To make the meringue, in a small bowl, whisk together sugar and cornstarch.
In a mixing bowl with whisk attachment, beat egg whites until foamy. Then slowly add sugar mixture one tablespoon at a time and continue to beat on medium high speed until hard peaks form. Transfer the meringue into a pastry bag, fitted with decorative tip. (I used Wilton 1M.)
To assemble the tartlets, drop about 1 tablespoon of raspberry sauce in each tartlet shell. Spread evenly.
Pipe the lemon curd filling over the raspberry sauce.
And finally, top with meringue. Broil the tartlets for 3-4 minutes (position the rack in the middle), or until nice and browned. Keep a close eye on it.