Pears:

Peel, core and slice the pears 1/2-inch thick. Combine the pears in a large saute pan with the sugar, Riesling, salt, and lemon juice. Cook over medium-high heat until the juices start to evaporate, 10 to 15 minutes. In a food processor, roughly puree the pears. Set aside to cool.

Riesling Sabayon:

Fill a medium saucepan 1/3 full of water. Bring the water to a low boil.

Fill a medium bowl with ice water. Set aside.

In a stainless steel bowl, whisk together the egg yolks, sugar, Riesling, and salt. Set the bowl into the pot of water, making sure that the water doesn't touch the bottom of the bowl. Cook, whisking constantly, until thick, about 3 minutes. Set the bowl in the bowl of ice water. Whisk until cool.

In a separate bowl, whisk the cream until soft peaks form. Fold it into the Riesling mixture. Refrigerate until you are ready to assemble the trifle.

Assembly:

Cut the genoise in half horizontally with a knife.

Pour 1/3 cup of the sabayon in the 2 1/2-quart glass bowl. Cut and fit pieces of the genoise over the sabayon in a single layer. Cover with 2/3 cup of the reserved puree, then 1 cup of sabayon. Continue layering in the same manner, ending with sabayon.

Refrigerate for at least 6 hours before serving.

This trifle can be made 1 to 2 days ahead.