Frozen puff pastry dough or home-made crust:
1 1/2 sticks (3/4 cup) cold unsalted butter
1 1/2 cups all-purpose flour
1/2 teaspoon salt
1 to 2 tablespoons ice water
Pie weights or raw rice for weighting shell
6 ounces feta
1 cup heavy cream
2 large eggs
For dough: Cut butter into bits. In a food processor pulse together flour, butter, and salt until most of mixture resembles coarse meal with remainder in small (roughly pea-size) lumps. Add 1 tablespoon ice water and pulse 2 or 3 times, or until just incorporated. Test mixture by gently squeezing a small handful: When it has proper texture it should hold together without crumbling apart. If necessary, add enough remaining water, 1/2 tablespoon at a time, pulsing 2 or 3 times after each addition until incorporated and testing, to give mixture proper texture. (If you overwork mixture or add too much water, pastry will be tough.)
Turn out mixture onto a work surface and divide into 4 portions. With heel of hand smear each portion once in a forward motion to help distribute fat. Gather dough together and form it, rotating it on work surface, into a disk. Chill dough, wrapped in plastic wrap, until firm, at least 30 minutes, and up to 1 day.
Preheat oven to 450°F. Trim beets, leaving about 1 inch of stems attached (reserve greens for another use). Wrap beets tightly in foil and in a baking pan roast in middle of oven until tender, about 1 hour.
While beets are roasting, on a lightly floured surface with a floured rolling pin roll out dough into a 12-inch round (about 1/8 inch thick). Fit dough into a 9-inch tart pan with a removable fluted rim. Roll rolling pin over top of shell to trim dough flush with rim. Chill shell until firm, about 30 minutes. Unwrap beets carefully. When beets are cool enough to handle, slip off skins and stems. Beets may be roasted 1 day ahead and chilled, covered.
Reduce temperature to 375°F. Line shell with foil and fill with pie weights or raw rice. On a baking sheet bake shell in middle of oven 30 minutes. Carefully remove weights or rice and foil and bake shell until just golden, about 10 minutes more. Cool shell in pan on a rack. Shell may be made 1 day ahead and kept in pan, covered, at room temperature.
Reduce temperature to 350°F. Thinly slice beets and arrange in shell. Crumble feta into small pieces and in a bowl whisk together with cream and eggs. Season egg mixture with salt and pepper and pour over beets. Bake tart in middle of oven until filling is set, about 20 minutes, and cool in pan on rack.
Source: Gourmet, 1998