Step 1Heat the oven to 350 degrees. Grease a 13-by-9-inch baking pan, line the bottom with parchment paper, then grease again.
Step 2In a large bowl, whisk together the flour, baking powder, baking soda and cinnamon, and set aside.
Step 3In a separate large bowl, beat together the eggs and sugar, then beat in the oil. Beat in the flour mixture just until combined, then fold in the pears and nuts.
Step 4Pour the batter into the prepared pan. Place the pan in the oven and bake until puffed and golden brown, and a toothpick placed in the cake comes out clean, about 1 hour and 20 minutes. Check the cake after an hour, and cover the top loosely with a sheet of foil if it browns too quickly before it is done.
Step 5Remove and cool completely on a rack before serving.