For the tartlet shells

1. Mix dough. In the bowl of an electric mixer fitted with a paddle attachment, mix the butter and sugar together until they are just combined. Mix in the vanilla. In a medium bowl, whisk together the flour and salt to remove any clumps. With the mixer on low speed, gradually add the flour/salt mixture to the butter/sugar mixture until the dough starts to come together.
2. Chill dough. Gather the dough together to form a ball and place it on a sheet of plastic wrap. Place another sheet of plastic wrap on top and flatten the ball into a 1/2 inch thick disk. Transfer the dough to the refrigerator and chill until firm, 45 minutes.
3. Prep oven and pan. When ready to bake the tartlet shells, heat oven to 350 degrees. Spray a 24-well mini-muffin pan with baking spray (this is very important).
4. Roll out dough. On a lightly floured surface, roll out dough to 1/8 inch thickness. Use a 2 1/2-inch diameter round cutter and cut out 24 rounds of dough, gathering scraps and re-rolling as necessary. Place a round of dough into each well of the prepared mini-muffin pan. Using your fingers, fit the dough to fit into the well; pleating the dough as necessary. If the dough becomes too soft to work with, chill it in the freezer for a few minutes until it is firm again. Using a small off-set spatula to lift the rounds of dough will also help.
5. Bake. Place muffin pan in freezer to chill dough until firm, 10 minutes. Place a mini-cupcake liner on top of each well of dough and fill it with rice or beans. Bake for 20 minutes, rotating the pan half way through. Remove the muffin liners and beans, and continue baking for another 4-5 minutes, or until lightly browned. Let tartlet shells cool in pan 5 minutes. Using the tip of a small paring knife to loosen the edges, gently remove the tartlet shells from the pan and allow to cool completely on baking rack. 

For the lemon curd

1. Mix ingredients. Combine the lemon zest and sugar in a food processor. Blend until the zest is very finely minced and blended into the sugar, about 30 seconds. Add the lemon juice, eggs, butter pieces, and salt. Blend again for an additional 30 seconds or until the mixture is well combined. The mixture will look curdled which is perfectly fine.
2. Cook lemon curd. Pour the mixture into a saucepan and place pan over medium-low heat. Cook the mixture, stirring constantly with a rubber spatula, until the curd thickens and the temperature reaches 175 degrees, about 10 minutes.
3. Cool. Remove from heat and let the curd cool to room temperature, stirring occasionally. Cover tightly and refrigerate until ready to use.

For serving

1. Prep cream. Whip the cream with the sugar until soft peaks form.  Set aside.
2. Assemble tartlets. Spoon lemon curd into the tartlet shells (about 1 1/2 teaspoons per tartlet) and top with a small dollop of whipped cream.