Heat the oven to 350 °F. Position an oven rack in the center of oven. Place the butter, and sugar in the bowl of an electric mixer fitted wtih the paddle attachment (a handheld mixer is fine; just allow a little extra time to reach each stage in the recipe). Beat on medium speed until the mixture is very light in color, about 3 to 4 minutes. Use a rubber spatula to scrape down the sides of the bowl. Add the almond extract and blend well, another 30 seconds. In a separate bowl, whisk together the flour and salt. Add the dry ingredients to the butter mixture and combine on a low speed just until the dough is thoroughly combined, about 30 to 40 seconds. Measure out 1/2 cup of the dough and set it on a small plate, then place the plate in the freezer (this will chill the dough and make it easier to crumble). Press the remaining dough into a 9 or 9 1/2-inch tart pan in an even layer (the edges can be a little higher than the rest, just be careful that the center is not the thickest point). If the dough is too sticky, just chill it briefly. Use a small offset spatula or the back of a spoon to spread the jam in a thin, even layer over the surface of the dough, leaving a border of about 1-inch around the edges. Remove the reserved dough from the freezer and crumble it into small pieces over the layer of the jam, allowing some of the jam to peek through. Sprinkle the sliced almonds evenly over the top of the tart. Bake for 40 to 50 minutes, or until the topping is a beautiful golden brown. Remove from the oven and place on a rack to cool completely. If your tart pan has a removable bottom, to unmold, center the tart pan on top of a large can so that it balances midair as the rim of the tart pan falls to the counter. Leave the bottom of the pan under the tart for support, or run a large spatula between the crust and the pan, using the spatula to guide the tart onto a plate. Alternately, cut wedges straight from the pan. Serve with tart whipped cream. Store the tart covered in plastic wrap, at room temperature for 3 to 4 days. The tart can be assembled ahead and frozen for up to 1 month. Assemble the tart, then wrap tightly twice in plastic wrap and freeze on a flat surface -- it may require a few minutes extra of baking time.
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