In a mixing bowl, combine all-purpose flour and salt. Cut in cold, unsalted butter until the mixture resembles coarse crumbs. Whisk together honey and cold water, then mix into the flour mixture until it just comes together. Shape into a disk, wrap, and refrigerate for 1 hour.

Preheat your oven to 350°F (175°C). Roll out the chilled dough into a 12-inch circle and fit into a 9-inch tart pan. Trim excess dough, prick the bottom, and bake for 10-12 minutes until slightly golden. Cool completely.

For the lemon curd, whisk together lemon juice, zest, eggs, honey, and salt in a saucepan. Cook over medium heat, stirring constantly until thickened (about 8-10 minutes). Remove from heat, stir in cold butter, and strain into a bowl.

Pour the lemon curd into the cooled crust, spreading evenly. Bake at 350°F (175°C) for an additional 8-10 minutes until the center jiggles slightly. Cool at room temperature for 30 minutes, then refrigerate until completely chilled.

Puree the blueberries in a blender and strain. Mix the puree with honey and cornstarch in a saucepan, heat over medium until thickened (about 5-7 minutes). Remove from heat and cool slightly.

Pour the blueberry filling over the lemon curd layer, spreading evenly. Refrigerate for at least 2 hours before slicing and serving.