| 1 | For the dough: combine dry ingredients in bowl of food processor and pulse several times to mix. |
| 2 | Cut butter into 8 pieces and distribute evenly over dry ingredients in work bowl. |
| 3 | Pulse until very finely powdered. |
| 4 | Add egg and continue to pulse until dough forms a ball that revolves on blade. |
| 5 | Remove dough, press into a disk, wrap and chill. |
| 6 | To poach the peaches: cut a cross in the blossom end of each peach and immerse in boiling water about 30 seconds. |
| 7 | Remove peaches to a bowl of ice water and slip off skins after they cool. |
| 8 | Cut each peach into eight wedges, cutting them away from the pit as they are removed. |
| 9 | Arrange slices in a wide, shallow non-reactive pan in one layer and sprinkle with sugar. |
| 10 | Cover and place over low heat and bring to a simmer. |
| 11 | Remove from heat. |
| 12 | Cool. |
| 13 | Drain peaches gently by lifting them from the juices with a slotted spoon to a plate or other non-reactive surface. |
| 14 | Reserve the juices for another use. |
| 15 | Sour cream filling: preheat the oven to 350f and set a rack in the lower third. |
| 16 | Roll the pastry dough on a floured surface and line a 10-inch tart pan with it. |
| 17 | Arrange the peach wedges on their sides in a concentric pattern. |
| 18 | Whisk the filling ingredients together, strain and skim foam from top. |
| 19 | Pour filling over peaches and sprinkle evenly with the sliced almonds. |
| 20 | Bake the tart about 40 minutes, until the crust is baked through and the filling has set. |
| 21 | Cool on a rack. |
| 22 | Unmold, and serve at room temperature. |
| 23 | Dust with the confectioners" sugar immediately before serving. |
| 24 | Store leftovers refrigerated |
