Preheat oven to 300 degrees. Lightly spray 3 – 9 inch cake pans with non-stick cooking spray.
In an electric mixer, fitted with a whisk attachment, beat the egg whites at medium speed until they start to foam. With the mixer still running, add the cream of tartar and salt. Turn the mixer up to high and gradually add the sugar. Continue beating until stiff peaks form and the sugar is completely dissolved. Test this by rubbing some of the egg white mixture between your thumb and forefinger. If it no longer feels gritty, you are done. Turn off mixer, add the vanilla and almond extracts, turn the mixer back up to high and mix until extracts are fully incorporated. Fold in the 1 1/2 cups ground almonds.
Divide the meringue batter evenly between the three prepared pans, smoothing the top with a spatula. Bake for 40 – 45 minutes or until the meringues are firm and lightly browned. Let cool in the pans for 1 hour.
While meringues are cooling, make the buttercream.
In an electric mixer fitted with a wire whisk attachment, whisk together the confectioners’ sugar and butter and salt, starting on low and gradually turning the speed up to medium. Continue beating for 3 minutes. Add the vanilla extract, lemon juice and 2 teaspoons of cream or orange liqueur and whisk for 1 more minute, adding more cream or liqueur if necessary until a creamy, spreadable consistency is achieved. With a spatula, fold in the apricot preserves. Refrigerate until ready to use.
Remove meringues from pans by flipping them over onto a counter and gently rapping them until they fall out.
To assemble, place one meringue on a serving platter. Spread a little less than a third of the buttercream over the meringue, top with another meringue, more buttercream and finally the last meringue. Frost the top and sides with the remaining buttercream.
Garnish the dacquoise by patting the sliced almonds around the sides, sticking them to the buttercream.