Measure the flour, salt and baking powder into a large mixing bowl. Add half of the butter bits and toss with the flour mixture. Using a pastry blender or a fork, cut the butter into the flour until it looks like cornmeal. Add the remaining butter and continue blending until the mixture looks like coarse cornmeal with pea-size lumps.  

Drizzle the ice water into the mixture, one tablespoon at a time. Stir after each spoonful of water. Test the consistency by squeezing a small portion in your hand. If it doesn’t hold together in a lump, continue adding and mixing ice water. When the mixture holds together after you squeeze it, stop adding water. You may think the pastry dough looks too loose and dry but as long as the squeeze test holds together in a lump it is exactly right. The less water you add, the more tender and flaky the crust will be. 

Tip the dough onto a work surface and push it together into a ball. Wrap the ball in plastic wrap and let it chill in the refrigerator for at least 30 minutes.  

Remove the dough from the fridge and let it rest on the counter about 30 minutes.

While the dough is resting, coat six, 4-inch, removable bottom tart pans with non-stick oil spray and reserve. 

Remove the plastic wrap from the dough and place it on a lightly floured work surface. With a sharp knife or bench scraper, cut the dough into 6 equal portions. Shape each portion into a ball.

Working with one portion at a time, flatten the ball and roll it into a 6-inch circle, lifting and turning the dough as you roll, dusting with additional flour as needed.

Lift the dough and place it into a prepared tart pan. Ease the dough next to the pan with your fingers without stretching it. Trim the excess by placing the rolling pin on top of the pan, pressing lightly.

Continue the process with the remaining dough balls until all the pans are lined and trimmed. Prick each tart on the bottom and sides with a fork. Place the tarts on a baking sheet or tray and place in the freezer for 30 minutes until firm.

Line each tart with a piece of foil, pressing tightly to the frozen pastry. Fill with pie weights, rice or beans and place the tarts on a sheet pan.  Transfer to the oven and bake for 20 minutes. Remove from the oven and remove the foil/weights.  Return the sheet pan to the oven and continue baking for an additional 10 to 15 minutes until the crusts are lightly golden. 

Remove the sheet pan from the oven and let the tarts cool before filling. 

Whisk the sugar, cornstarch and salt into a medium saucepan until combined. Add the lemon zest and, using your fingers, rub the zest into the sugar mixture. This will release the oils in the zest and enhance the lemon flavor. 

Add the water to the sugar mixture and whisk until well blended. Whisk in the egg yolks and the lemon juice.

Set the pan over medium heat, and stir continuously until the mixture begins to bubble and thicken. Be patient, this will take about 8 to 10 minutes. Reduce the heat to low and simmer an additional 3 minutes, stirring continuously. 

Remove the saucepan from the heat and stir in the butter until completely melted.  

Spoon the hot mixture into each cooled tart shell and smooth the top. Place the tarts on a wire rack to finish cooling.  

Place the sugar and cornstarch in a small bowl and whisk to combine. Reserve.

Add the egg whites and salt to a large mixing bowl. Using the whisk attachment, beat on high speed until foamy. Slowly, begin adding the sugar mixture 1 tablespoon at a time while continuing to whip on high speed until they reach stiff peaks. 

Spoon the meringue into a pastry decorating bag with a decorative tip and pipe dollops onto the lemon filling.  

Set the oven to “Broil” and allow to heat for 5 minutes with the oven rack at the upper third position, about 8 inches from the element.

Place the tarts on a sheet pan and broil for 1-2 minutes, turning the pan occasionally to toast the tarts evenly.  

Remove the sheet pan when the tarts are toasted to your liking and place on a wire rack to cool, then transfer to the refrigerator to finish cooling.