For the Pears:
2/3 cup sugar
1/2 cup white wine
1/2 cup Marsala (or other sweet fortified wine, such as Port or Madeira)
1 cup water
1/2 tsp vanilla extract
5 medium pears, peeled, halved and cored
For the Cake:
1 1/2 cups finely ground hazelnuts (traditional) or almonds (also good)
1/2 cup flour
1/2 tsp baking powder
1/2 tsp salt
1/2 cup unsalted butter, at room temperature
1/2 cup sugar
1/2 tsp vanilla
Preheat the oven to 350 degrees, and grease a 9-inch pan (a springform is nice if you have it, but anything will work).
Combine the sugar, wines, water, vanilla and pears in a saucepan. Bring to a simmer, and then reduce heat to low. Simmer, uncovered, until the pears just begin to get translucent, and are tender when pierced with a fork (about 30 minutes). Remove pears from the poaching liquid, and set aside to cool. Continue simmering the poaching liquid to reduce (more on that later).
In a large bowl, sift together the nut meal, flour, baking powder, and salt. If the nut meal isn't ground finely, you can either sift through a larger amount of nut meal to yield 1 1/2 finely-ground cups, or leave as is for a more rustic cake. Set aside.
Cream the butter and sugar until light and fluffy. Add the eggs, one by one, beating well after each addition. Add vanilla, mix well. Fold in the dry ingredient mixture, stirring until just combined. Spread the batter into the prepared pan. Place the poached pears, cut side down, on top of the cake in a pretty pattern. Bake until a tester inserted in the center comes out clean, about 30-40 minutes. Remove from the oven.
While the cake is baking, continue simmering the poaching liquid until it has reduced to about 1/2 cup (it will be thick and syrupy, and the color will have darkened). When the cake is out of the oven, brush it with this syrup, covering both the cake and the pears. Wait a moment for the syrup to be absorbed, and then repeat. Serve warm or at room temperature.