In a food processor, combine the flour, cheese, lemon zest, black pepper, and 1 teaspoon salt. Process until combined. Add the butter and pulse until the dough resembles coarse crumbs. Add the sour cream, egg yolk and pecans and pulse again until just incorporated. Add lemon juice and pulse again. When the dough holds together, dump it onto a lightly floured surface and press it into a flat disk. Wrap in plastic wrap and chill for 2 hours or up to 2 days.
Position rack in the center of the oven and heat the oven to 375 degrees.
On a lightly floured surface, roll out the disk to just under 1/8” thick and use a cookie cutter to stamp out 1 ½” or 2” rounds. Arrange the rounds on an ungreased baking sheet.
Bake until nicely browned around the edges and no longer doughy in the center, about 15 minutes. Use a spatula to carefully transfer the crackers to a rack and let cool. Serve immediately or store in an airtight container for up to 5 days.
Yields 5 dozen