Position racks in upper and lower thirds of oven; preheat to 300 degrees F. Coat 2 large baking sheets with cooking spray.

Mix flour, sugar, butter, orange zest, orange juice and vanilla in a medium bowl until smooth. Spread 1 tablespoon of batter into a 2 1/2-inch circle on the prepared baking sheet. Repeat with the remaining batter, making 6 cookies per baking sheet, spacing them about 4 inches apart.

Bake the cookies until lightly browned around the edges, switching the pans back to front and top to bottom once halfway through, 16 to 18 minutes. Immediately and carefully transfer the cookies from the pan to a wire rack using a thin metal spatula. Let cool completely.

Notes: White whole-wheat flour is light in color and flavor but has the same nutritional properties as regular whole-wheat flour. It can be ordered from the King Arthur Flour Baker's Catalogue at shop.bakerscatalogue.com. Whole-wheat pastry flour can be substituted. Find whole-wheat pastry flour in the natural-foods section of large supermarkets and natural-foods stores.

To make your own citrus fruit salad, remove the skin and white pith from oranges and grapefruit with a sharp knife. Working over a bowl, cut the segments from their surrounding membranes. Squeeze juice in the bowl before discarding membranes. Toss the segments with citrus zest if desired. Or look for jarred prepared fruit salad in the market's produce section.

MAKE AHEAD TIP: Store cookies in an airtight container, with parchment or wax paper between layers, for up to 2 days.