PreparationFor crust: Coat springform pan with nonstick spray. Whisk flour, cornstarch, and salt in a small bowl; set aside. Place butter and powdered sugar in a food processor. Pulse until mixture is smooth. Add dry ingredients to food processor and pulse until mixture resembles medium-size pebbles (dough will not come together completely). Transfer dough to prepared pan. Using your fingers, press dough evenly onto bottom and 1 1/2" up sides of pan. DO AHEAD: Crust can be prepared 1 day ahead. Cover and chill. For filling and assembly: Using a mandoline, slice lemon into paper-thin rounds. Remove seeds. (If using a regular lemon, blanch slices in boiling water for 4 minutes, drain, and let cool before proceeding). Mix sugar, honey, and lemon zest in a medium bowl. Add lemon slices and toss to coat. Let sit until lemon is softened and sugar is dissolved, 30-45 minutes. DO AHEAD: Lemon slice mixture can be made 1 day ahead. Cover and chill. Place rack in upper third of oven; preheat to 325°F. Bake crust until center is firm to the touch and edges are beginning to turn golden brown, 30-35 minutes. When crust is almost done baking, whisk eggs and egg yolks in a medium bowl to blend. Whisk flour, cornstarch, and salt in a small bowl; add to egg mixture and whisk to combine. Whisk in lemon juice. Add lemon slice mixture; mix gently to combine. Reduce oven temperature to 300°F. Pour filling into hot crust. Bake until filling is set and slightly puffed around edges, 25-30 minutes. Transfer pan to a wire rack; let cool completely. Chill for at least 4 hours, then unmold. Serve cold. DO AHEAD: Tart can be made 2 days ahead. Cover and keep chilled.
PreparationFor crust: Coat springform pan with nonstick spray. Whisk flour, cornstarch, and salt in a small bowl; set aside. Place butter and powdered sugar in a food processor. Pulse until mixture is smooth. Add dry ingredients to food processor and pulse until mixture resembles medium-size pebbles (dough will not come together completely). Transfer dough to prepared pan. Using your fingers, press dough evenly onto bottom and 1 1/2" up sides of pan. DO AHEAD: Crust can be prepared 1 day ahead. Cover and chill. For filling and assembly: Using a mandoline, slice lemon into paper-thin rounds. Remove seeds. (If using a regular lemon, blanch slices in boiling water for 4 minutes, drain, and let cool before proceeding). Mix sugar, honey, and lemon zest in a medium bowl. Add lemon slices and toss to coat. Let sit until lemon is softened and sugar is dissolved, 30-45 minutes. DO AHEAD: Lemon slice mixture can be made 1 day ahead. Cover and chill. Place rack in upper third of oven; preheat to 325°F. Bake crust until center is firm to the touch and edges are beginning to turn golden brown, 30-35 minutes. When crust is almost done baking, whisk eggs and egg yolks in a medium bowl to blend. Whisk flour, cornstarch, and salt in a small bowl; add to egg mixture and whisk to combine. Whisk in lemon juice. Add lemon slice mixture; mix gently to combine. Reduce oven temperature to 300°F. Pour filling into hot crust. Bake until filling is set and slightly puffed around edges, 25-30 minutes. Transfer pan to a wire rack; let cool completely. Chill for at least 4 hours, then unmold. Serve cold. DO AHEAD: Tart can be made 2 days ahead. Cover and keep chilled.