Beat together butter and sugar with an electric mixer at medium speed until pale and fluffy, about 3 minutes. Beat in egg and vanilla. Reduce speed to low and mix in flour, salt, and lemon zest until mixture just forms a dough. Shape dough into 2 balls, 1 slightly larger than the other. Flatten each ball into a 5-inch disk, then wrap each in wax paper and chill 30 minutes. Stir together preserves, lemon juice, and extract in a small bowl. Roll out thicker piece of dough (keep remaining piece chilled) between 2 sheets of wax paper into an 11-inch round. Remove top sheet of paper and invert dough into a 9- by 1-inch fluted round tart pan with a removable bottom. Peel off paper and fit dough into pan, trimming side to 1/4 inch below top of rim. Chill shell. Roll out remaining dough in same manner and remove top sheet of paper, then cut dough into 10 (1-inch-wide) strips. Slide strips on wax paper onto a baking sheet and chill until firm, about 10 minutes. Preheat oven to 375 degrees. Spread apricot filling in tart shell and arrange 5 strips across filling (about 1 inch apart), trimming excess dough at ends of strips. Arrange remaining 5 strips on top (about 1 inch apart) to form a lattice (do not weave), trimming ends. Press ends onto edge of tart shell and bake tart in middle of oven until golden, 40 to 50 minutes. Cool completely in pan on a rack.
Ready in 3 1/4 hr