Start by making the crust. Preheat the oven to 350 degrees F. Line an 8x8 square baking pan with parchment paper and set aside.
In a stand-up mixer with the paddle attachment, beat the butter, sugar, and lemon zest together until smooth and creamy. Add flour and mix until well incorporated. You should have a thick dough that holds together when pressed between your fingers.
Press the dough into the prepared pan and bake for 20 minutes until light golden brown. Remove from the oven and let cool for at least 15 minutes.
Next, make the lemon curd filling. In a food processor combine the tofu, lemon juice, zest, and granulated sugar and process until smooth and creamy, scraping down the sides as necessary. Add the powdered sugar, cornstarch, and vanilla extract and process again until combined.
Pour the lemon curd into the cooled crust and bake for another 25-35 minutes until the lemon curd has set. It should have a slight wobble to it.
Once cooked, remove from oven and let cool at room temperature for 20 minutes before placing them in the refrigerator to cool all the way. Don't skip this step. It is necessary for the lemon bars to set properly.
Once set, dust with powdered sugar or candied lemon slices just before serving.