Add the flour, sugar, baking powder, salt and baking soda in a food processor for 30 seconds to combine. Add the frozen butter and pulse until the size of small peas. Do not over mix. Add the buttermilk and almond extract and pulse just until the dough holds together when pinched. Form the dough into a disk and wrap in plastic wrap or wax paper, lightly dusted with flour. Refrigerate 1 hour.
For the Cream:
Whisk the egg white with the confectioners' sugar until frothy. Add the ground almonds, melted and cooled butter and the almond extract. Whisk until blended and refrigerate until needed.
For the Filling:
Peel and core the pears. Cut into ¼ inch slices and toss in a bowl with the lemon juice and lemon zest. Set aside.
Preheat the oven to 400°F. Lightly dust a sheet of parchment paper with flour and place the dough on top. Sprinkle lightly with flour and top with another sheet of parchment paper. Roll out the dough to a 12-inch circle. Peel off the top layer of paper and invert the dough onto a baking sheet lined with a third piece of parchment. Spread the cream mixture over the dough leaving a one-inch border. Arrange the pear slices in concentric circles over the cream. Blend the cinnamon and sugar together and sprinkle on top of the pears. Fold the edges of the dough over the pears. Crimp edges if needed to seal. Sprinkle small bits of butter over the filling. Bake 20 to 25 minutes or until pears are tender and the crust is lightly browned. Remove the Galette from the oven and preheat the broiler. Cover the crust with foil and glaze the pears about 6 inches from the heat for about 1 minute or until the pears are golden brown. Cool on the baking sheet 5 minutes. Transfer to a wire rack and cool completely. Sprinkle with confectioners' sugar and cut into wedges to serve.
Nutrition information is calculated using an ingredient database and should be considered an estimate. When multiple ingredient alternatives are given, the first listed is calculated for nutrition. Garnishes and optional ingredients are not included.