Glazed with honey, blueberries are glossy, juicy beads atop a lemon-flavored tart.The airy, souffle-like filling is made with meringue and pastry cream.
Preheat oven to 375 degrees. Place a 9-inch cake ring on a rimmed baking sheet lined with parchment. Roll out dough between sheets of parchment to an 11-inch circle (1/8 inch thick). Refrigerate 15 minutes. Peel off parchment; press dough into ring. Trim flush with top edge of ring. Refrigerate until cold, about 30 minutes.
Prick dough all over with a fork. Line tart shell with parchment, and fill with pie weights or dried beans. Bake until crust starts to turn golden, 20 to 25 minutes. Remove parchment and weights; continue baking until pale golden, about 5 minutes more. Let cool on a wire rack.
Whisk together 1/4 cup sugar, the flour, and a pinch of salt; set aside. Whisk buttermilk and yolks in a small saucepan over medium-low heat; gradually whisk in sugar mixture. Cook, whisking constantly, until thickened, 5 to 7 minutes. Stir in vanilla, zest, and juice. Transfer to a medium bowl set in an ice-water bath. Let cool completely, stirring occasionally.
Meanwhile, put whites and cream of tartar in the bowl of an electric mixer fitted with the whisk attachment. Add a pinch of salt. Beat on low speed until foamy. With mixer running, gradually add remaining 1/4 cup sugar. On medium-high, beat until stiff, glossy peaks form.
Gently fold pastry cream and 1 cup berries into meringue. Pour mixture into tart shell, making swirls and peaks. Bake until golden, 40 to 45 minutes. Let cool on a wire rack. Remove cake ring.
Meanwhile, heat remaining cup berries and honey in a medium skillet over medium-low heat, stirring gently, until just warm, about 2 minutes. Spoon glazed berries over tart.