Position rack in center of oven; preheat to 350°F. Coat 2 large baking sheets with cooking spray or line with parchment paper.
Whisk whole-wheat flour, all-purpose flour, baking powder and salt in a large bowl. In another large bowl, whisk eggs and 1 cup sugar until combined. Add oil and vanilla; whisk to combine. Stir in the dry ingredients and walnuts with a spoon until just combined.
Combine the remaining 1 tablespoon sugar and cinnamon in a small bowl. With lightly oiled hands, divide the dough in half and spread it into two 3-by-12-inch-long logs on one of the prepared baking sheets. The logs of dough will be side by side and about 3/4 inch thick each. ("Don't potchke the dough.")
Bake until lightly browned on the edges and beginning to firm, 20 to 30 minutes. Cool on the pan on a wire rack for 20 minutes. (Keep the oven on.) Slice each log into 1/2-inch-thick cookies; divide the cookies between the baking sheets, cut-side down, and sprinkle with half the cinnamon-sugar mixture.
Move the racks to the top and bottom thirds of the oven. Bake the cookies for 5 minutes. Turn the cookies over, sprinkle with the remaining cinnamon-sugar mixture and bake for 5 minutes more. Transfer to a wire rack to cool completely.