Preheat oven to 350°F.   Line the bottom of a 9-inch springform pan with parchment paper.   Butter the sides of the pan.

Peel, halve, and core 3 of the apples, and cut each half into 6 even slices.  Toss the apple slices with half of the lemon juice and set aside.

Peel, halve, and core the remaining apples.   Cut into 1/3-inch dice.  Toss with the remaining lemon juice and set aside.

Grate the almond paste and place it in the bowl of a stand mixer fitted with the flat beater attachment.  Add the salt and melted butter; beat for 1 to 2 minutes, until smooth.  Then beat in the sugar and almond extract.  Beat in the eggs, one at a time, beating for 30 seconds after each addition.  Scrape down the sides of the bowl.

In a separate bowl, whisk together the flour, cornstarch and baking powder.  Add to the almond batter and beat until well blended.  Then fold in the diced apples.  Scrape the batter into the prepared pan and smooth the top.  Distribute the sliced apples decoratively in concentric rings on the top of the cake.  Then, using the flat of your hand, gently push the apples into the batter; they should not be submerged, just lightly anchored.

Place the pan in the oven and bake for 1 hour and 10 minutes, or until the top is golden brown and a tester inserted into the middle of the cake comes out clean.  Remove the pan from the oven and place on a rack to cool.

Immediately heat the apricot jam over medium-high heat until just bubbling.  Brush a thin layer of the hot jam over the still-hot cake.  Let cool completely before removing the springform ring.  The cake will keep at room temperature, lightly wrapped in plastic wrap, for several days.