FOR THE DOUGH: In a medium bowl, whisk together the flour, sugar, baking powder, zest & salt, then with a pastry cutter, cut in the butter until the mixture resembles coarse crumbs.
In a small bowl, whisk together the ricotta cheese, egg yolk, water & vanilla extract, then add this mixture to the flour mixture & stir with a fork just until the dough begins to come together when a small bit is pressed between your fingers.
Shape the dough into a disk, then wrap in wax paper & refrigerate for at least 2 hours or up to 2 days.
Position a rack in the middle of the oven & preheat the oven to 350 degrees F, then generously butter a large baking sheet.
Place the dough on a lightly floured sheet of wax paper, then top that with another sheet of wax paper & roll out the dough to a 10-inch circle.
Remove the top sheet of paper, transfer the dough, paper side up, to the prepared baking sheet, & then remove the remaining sheet of wax paper.
Fold in the edge of the dough to make a 1/2-inch rim, before baking the crust for 15 minutes.
FOR THE FILLING: Meanwhile, in a medium bowl, toss together just 2 pints of the blueberries with the sugar & zest, then pour this mixture onto the warm crust.
Bake for another 45 minutes, then top the pizza with the final 1/2 pint of berries & bake 10 minutes longer.
Remove the pizza from the oven & put the baking sheet with the pizza on a wire rack to cool for at least 5 minutes.