In a bowl, beat the egg yolks and the sugar together until the grittiness of the sugar is gone and the mixture is noticeably lighter in color. Then beat in the buttermilk, vanilla, almond extract, and cinnamon.
Add the flour and whisk lightly, but leave small lumps of flour in the batter.
In a clean bowl with clean beaters, beat the egg whites and the cream of tartar into a soft-peaking froth. With a rubber spatula, mix this into the batter, but don't overmix--streaks are okay.
Generously butter a 10-inch cake pan. Distribute the pear chunks on the bottom, and pour the batter over it.
Bake at 400 degrees for eight minutes, then lower the oven to 325 degrees and continue baking for another 20 minutes. The clafoutis is ready when barely browned on the top.
