Panforte is a kind of Italian cake, originating in Siena, and as such it is sometimes referred to as Siena cake. It contains a lot of nuts and candied citrus peel, and a lot of spices, and very little actual cake. It's a lot like fruitcake, except more so. It used to be eaten for health and strength, and later became a Christmas cake. Nowadays it's eaten year-round as a dessert cake, or as a accompaniment to wine, tea, or coffee.
Pan Forte means 'strong bread' in Italian, referring to the strong flavor. The first record of panforte appeared in 1205, where it was referred to as "panes pepatos et melatos" (bread of peppers and honey), and was part of a tax payment to the local nuns. In those days, panforte was even stronger, and did indeed include real pepper. Modern panfortes may include a pinch of pepper in their mix of spices, but most recipes no longer include this.
Local legend has it that when Queen Margaret of Savoy visited Siena, the master of ceremonies was worried that 'panpepato' would be too strongly flavored for Her Majesty. So he instructed the cooks to add pumpkin to the recipe, and replace the pepper with vanilla. This version is called Panforte Margaret, and closely resembles the panforte of today.
Legend also has it that panforte is an aphrodisiac.
I've never made it myself, so I'll not node a recipe, but a standard panforte includes 5-6 cups of nuts and cut up candied orange and lemon peel for each cup of flour. It includes spices such as cinnamon, nutmeg, cloves, coriander, and black pepper. It will likely also have some butter, sugar, and honey to help hold it all together. When panforte is taken out of the oven, it is dusted with confectioner's sugar and cinnamon. Panforte lasts forever, and should age few days (at least) before actually being eaten.