- First, make the dough: combine the flour, sugar, and salt in the bowl of a food processor, then scatter the butter/margerine pieces over the top. Pulse the machine 8 or 9 times, just until the butter/margerine is broken into fine pieces. Do not over-blend it.
- In a measuring cup with a spout, stir together the water and sour cream. Drizzle the liquid evenly over the flour mixture. Pulse the dough for about 8 short bursts, just until large, packable crumbs form.
- Dust your hands with flour. Turn the crumbs onto the counter and pack the dough together as you would a snowball.
- Place the dough onto a large sheet of plastic wrap and flatten it into a 3/4-inch-thick disk. Wrap it in the plastic and refrigerate it for at least 1 hour
- Get out a large, heavy cookie sheet, preferably one that’s shiny and at least 14 by 16 inches in size. Cut a piece of parchment paper to fit it and set the paper aside. Put the cookie sheet in the refrigerator for at least 30 minutes.
- Remove the chilled dough from the fridge and place it on the parchment. Dust your rolling pin and the dough with flour as needed to prevent sticking, then roll the pastry into a circle roughly 13 1/2 inches across
- Place the dough and parchment onto the sheet, and place the sheet back in the refrigerator. Move an oven shelf into the center position and heat the oven to 375°.
- Make the filling: quarter and core 3 of the peeled apples. With a sharp knife, slice the apples thinly — 1/8-inch thick or so. If a child is helping with this step, supervise her closely. Put the slices into a bowl and sprinkle them with the lemon juice. Toss the slices so they’re coated and set them aside.
- Quarter and core the remaining 2 apples. Cut them into1/4-inch-thick slices, then cut up the slices into fairly uniform 1/4-inch cubes. Place 2 1/2 cups of diced apples in a mixing bowl. Add 1/4 cup of the sugar, the cornstarch, and the cinnamon, and stir well.
- Put the apricot preserves in a small bowl and stir them briskly with a spoon to smooth out any lumps. Remove the dough from the refrigerator and dot it with the preserves. Use the back of a spoon to gently spread the preserves over the dough, being careful not to tear it. Sprinkle the bread crumbs evenly over the preserves.
- Pour the diced apples onto the center of the pastry and spread them very evenly across the surface, leaving about a 1 1.2-inch margin of dough at the edge.
- On top of the diced apples, arrange an overlapping row of apple slices in a circle, making sure the circle isn’t as wide as the diced apples. (This way, the slices won’t poke through the pastry when you fold it up.) Arrange a second circle of slices inside the first, then a third circle for the center of the blossom. Put the tart back in the fridge for 10 minutes to re-firm the pastry.
- Remove the tart from the refrigerator and sprinkle 1 tablespoon of sugar evenly over the apples. Using the parchment to help you handle the dough, fold the dough in sections up and over the edge of the filling. The dough will form pleats naturally as you make the folds. If the dough tears, just pinch it back together.
- Bake the tart on the center oven rack until it’s golden brown and bubbly, about 45 minutes to 1 hour. At the 30-minute mark, turn the sheet 180 degrees so that the tart bakes evenly.
- Remove the tart from the oven. Heat the apple jelly in a microwave until it melts, about 40 seconds. Use a pastry brush to paint the top of the apples with the jelly. Cool the tart on the sheet for at least 30 minutes before slicing. Makes 12 servings.