While your crust is baking, whisk together the granulated sugar, salt, lemon zest, and cream of tartar (if using). Add the whole eggs and yolks and whisk them in until the filling is smooth and uniform. Then pour in the lemon juice and whisk well. Finally, add the raspberries and mix in.
Pour the filling into a medium saucepan and begin heating the curd over medium low heat, stirring frequently. Continue stirring and heating until your curd has become quite thick, is steaming hot, and has reached 165-170F. This should take about 8 minutes. If your curd is not starting to thick after about 5 minutes, carefully notch the heat up a little bit.
Strain the thickened curd through a fine mesh strainer onto the browned crust. Bake the bars for 8-12 minutes, or until the filling is set and firm.
Cool the bars completely to room temperature, about 1 1/2 hours, then chill them in the refrigerator for another hour. (This makes them easier to cut cleanly.)