01 - Pulse the flour, salt, cayenne, and black pepper in a food processor until thoroughly combined.
02 - Add cold diced butter and pulse until mixture resembles coarse crumbs.
03 - Add grated cheddar and pulse until dough comes together. If too crumbly, add 1-2 teaspoons cold water as needed.
04 - Turn dough onto parchment paper and shape into a 1 1/2-inch diameter log. Wrap tightly and refrigerate for at least 1 hour until firm.
05 - Preheat oven to 375°F and line a baking sheet with parchment paper.
06 - Cut chilled dough into 1/4-inch rounds and arrange on prepared baking sheet, spacing 1 inch apart.
07 - Sprinkle with poppy seeds or sesame seeds if desired.
08 - Bake for 12-15 minutes until edges are golden.
09 - Cool on baking sheet for 5 minutes, then transfer to wire rack to cool completely.