How to Make It
To prepare crust, lightly spoon flour into dry measuring cups; level with a knife. Place flour, 1/2 teaspoon sugar, and salt in a food processor; pulse 2 times or until combined. Add butter and oil; pulse 5 times or until mixture resembles coarse meal. Drizzle flour mixture with water and vinegar; pulse 10 times or just until combined. Gently press mixture into a 3-inch circle on plastic wrap, and cover and chill for 30 minutes.
Preheat oven to 425°.
Slightly overlap 2 sheets of plastic wrap on a slightly damp surface. Unwrap and place chilled dough on plastic wrap. Cover with 2 additional sheets of overlapping plastic wrap. Roll dough, still covered, into a 10-inch circle. Fit dough, plastic wrap side up, into a 9-inch round removable-bottom tart pan. Remove remaining plastic wrap. Press dough against bottom and sides of pan. Pierce bottom of dough with a fork. Line bottom of dough with a piece of parchment paper; arrange pie weights on paper. Bake at 425° for 16 minutes or until edge is lightly browned. Remove pie weights and parchment paper; bake an additional 5 minutes or until bottom of crust is lightly browned. Cool on a wire rack.
Reduce oven temperature to 350°.
To prepare filling, combine rind, juice, egg yolks, and milk, stirring with a whisk until well blended. Pour into prepared crust. Bake at 350° for 15 minutes or until set. Remove tart from oven; place on a wire rack.
Increase oven temperature to 425°.
To prepare meringue, place cream of tartar and egg whites in a large bowl; beat with a mixer at high speed until foamy. Add 1/4 cup sugar, 1 tablespoon at a time, beating until stiff peaks form; beat in vanilla. Spread meringue evenly over filling, sealing to edge of crust. Make peaks with the back of a spoon (shown here). Bake at 425° for 4 minutes or until golden brown. Serve chilled or at room temperature.