Cut 1 lemon in half. Into a medium sized saucepan, juice the lemon and then add the lemon halves. Fill the pot halfway with water.
Snap off the thick fibrous outside leaves of the artichokes until you reach the pale yellow inner leaves. With a bread knife, cut off the top 1/3 of the artichoke and trim the stems of any dried unattractive ends. Place in the lemon/water pot as you go–this keeps the artichokes from turning brown. Alternatively, add the frozen artichoke hearts to the pot.
In the pot, add 1 cup of sugar and stir well to dissolve. Add more water if needed to cover the artichokes.
Place the pot over high heat with the lid on and bring to a boil. Reduce to simmer and place the lid ajar. Simmer until the artichoke hearts are very tender, about 1 hour. Cool in the cooking liquid. Discard the lemon halves and drain the artichokes. Pick over them for any lemon seeds. Place in a container in the refrigerator until ready for use.
Combine the flour, 1/2 cup sugar, butter, eggs and salt in a bowl. Blend using a hand-held pastry blender or a stand mixer until dough is formed. Avoid over-mixing. Use your hands to gather up the dough into a ball.
Place the ball between two large sheets of wax paper and flatten into a disk with the palm of your hand. Refrigerate for 1 hour.
In a bowl, add the ricotta, 1 cup of sugar the grated skin of 1 lemon (use the juice of the lemon for another purpose). Whisk until well combined. Add the reserved artichoke hearts and stir to combine.
Remove the dough in the wax paper from the fridge and place on a wooden board. Remove a golf ball-sized chunk of dough for the lattice and place back in the fridge.
Quickly roll out the dough to slightly larger than the size of the tart pan (to a thickness slightly less than a ¼ -inch). Peel away one sheet of the wax paper and invert the dough on the tart pan.
Gently press the dough into place patching up any holes. Tear away extra dough and reshape the circle to the shape of the tart pan.
Pour the prepared artichoke-and-ricotta mixture to the tart pan, and smooth into corners.
Sprinkle a little flour on the board. Remove the remaining dough from the fridge. Roll the dough on the board and cut into 1/2-inch strips with a pastry cutter. Create a “lattice” over the filling in the tart pan.
Place on the middle rack of the oven and bake for about 30 minutes, until the crust is lightly browned.
Remove to a cooling rack and cool completely. Remove the tart from the pan, slice and serve.