Make the crust: Pulse the flour, sugar and salt in a food processor. Add half of the butter and pulse until the mixture looks like coarse meal. Add the remaining butter and pulse into pea-size pieces. Add 1 egg, the lemon juice and 3 tablespoons ice water and pulse until the dough clumps together but has not yet formed a ball. Turn out the dough onto a piece of plastic wrap; press into a disk and wrap. Refrigerate until firm, at least 1 hour or overnight.
Preheat the oven to 400 degrees F and line a baking sheet with parchment paper. Roll out the dough into a 12-inch round on a lightly floured surface. Transfer the dough to the prepared baking sheet and refrigerate, 10 minutes.
Meanwhile, make the filling: Toss the nectarines with the honey, flour, vanilla and rosemary in a large bowl. Spoon the nectarine mixture onto the dough, leaving about a 3-inch border. Fold the edge of the dough over the fruit by about 2 inches, pleating as needed. Lightly beat the remaining egg with 1 teaspoon water. Brush the dough with the egg wash. Refrigerate until firm, about 20 minutes.
Scatter the butter over the fruit. Bake until the crust is golden brown and the filling is bubbling, 40 to 45 minutes. Let cool on the baking sheet. Serve with ricotta and honey.