These golden-brown biscuits make a perfect accompaniment to soups and salads.
In a small skillet over medium-high heat, coast the pumpkin seeds, shaking the pan frequently until they are golden brown and begin to pop, about 6 minutes. Set aside.
Heat the oven to 400 degrees. Line an 11-by-17-inch baking sheet with parchment paper, and set aside.
In a large bowl, combine the flour, salt, baking powder, cream of tartar, and sugar. Using your fingers or a pastry cutter, cut the butter into the flour mixture. Combine until the mixture resembles coarse meal. Carefully mix in the buttermilk just until it is incorporated. The mixture should appear crumbly.
Turn out the dough onto a lightly floured clean work surface. Lightly press the dough together to form a 3/4-inch-thick disk. Using a 2-inch-round biscuit cutter, cut out 12 biscuits, and transfer them to the prepared baking sheet. Using a pastry brush, lightly coat the tops of each biscuit with egg white, and sprinkle with the reserved pumpkin seeds. Bake until golden brown, about 12 minutes. Serve warm.