Preheat oven to 450°. Spray a 12-cup muffin pan with cooking spray.
In a colander or fine-mesh sieve set over a large bowl, toss together zucchini and ½ teaspoon salt; let stand for 15 minutes. Place zucchini in paper towels, squeezing to release excess liquid.
In a large bowl, whisk together flour, onion powder, all pepper, and remaining ½ teaspoon salt. Using a pastry blender or 2 forks, cut in cold butter until butter is pea-size. Stir in buttermilk just until combined. Stir in zucchini, 1 cup cheese, and chives just until combined. Divide batter among prepared muffin cups (about ¼ cup each).
Bake for 10 minutes. Sprinkle with remaining ¼ cup cheese. Bake until a wooden pick inserted in center comes out clean, 10 to 12 minutes more. Let cool in pan for 10 minutes; serve warm.
Recipe by Paula Deen Magazine at https://pauladeenmagazine.com/zucchini-cheddar-biscuits/