Line a baking sheet with parchment paper.
In a large bowl, whisk together flour, salt, baking powder, sugar, poultry seasoning, garlic powder, and pepper. Add cold butter, tossing to coat. Using a pastry blender or your hands, cut in butter until mixture is crumbly and butter pieces are pea-size. Stir in cranberries, cheese, and sage. Add buttermilk; stir with a fork until a shaggy dough forms. (Do not over mix.)
Turn out dough onto a lightly floured surface. (Dough will be crumbly and almost dry.) Pat dough into a rectangle about 1 inch thick. Using a lightly floured rolling pin, roll dough into a 15x6-inch rectangle. Using a bench scraper, fold dough in thirds like a letter. Rotate dough 90 degrees. Repeat rolling, folding, and rotating three more times. (Dough will seem too shaggy to do this to start but will come together and be easier to work with as you go.)
Roll dough into a 10x9-inch rectangle (about ¾ inch thick). Place on prepared pan. Cover and refrigerate until butter is chilled, at least 20 minutes.
Spray a 12-cup Bundt pan with baking spray with flour.
In a medium skillet, melt 1 tablespoon of softened butter over medium-high heat. Add celery and onion. Cook, stirring frequently, until tender and fragrant, 5 to 6 minutes. Remove from heat; stir in remaining 4 tablespoons of room temperature butter until melted. Transfer mixture to a large bowl; let cool for 5 minutes.
Cut dough into 1-inch squares, and add to vegetable mixture. Gently toss until combined and dough is evenly coated. Arrange dough pieces in prepared pan, lightly pressing dough into grooves of pan. Once all dough is in pan, lightly press with your hands to level dough and fully adhere. Freeze until firm, at least 20 minutes.
Preheat oven to 400°F (200°C).
Bake for 10 minutes. Reduce oven temperature to 375°F (190°C), and bake until golden brown and an instant-read thermometer inserted in center registers 190°F (88°C), 25 to 30 minutes more. Let cool in pan for 10 minutes. Invert loaf onto a serving plate. Garnish with cheese, if desired. Serve warm.
