Preheat oven to 350°F (177°C). Spray a 9×5-inch loaf pan with nonstick spray.

Whisk the flour, sugar, and cinnamon together in a medium bowl. Cut in the cold butter with a pastry cutter, your hands, or two forks until mixture resembles pea-size crumbs. It’s important to keep the streusel cold, so place in the refrigerator (covered or uncovered) until ready to use in step 4.

Whisk the flour, baking soda, and salt together in a large bowl. In a medium bowl, whisk the egg, brown sugar, and granulated sugar together until combined. Whisk in the buttermilk, oil, vanilla, and orange zest. Pour the wet ingredients into the dry ingredients, then whisk to completely combine. Avoid over-mixing. Fold in the cranberries and nuts (if using).

Pour the batter into prepared loaf pan. Top evenly streusel, pressing the streusel down gently into the top of the bread so it sticks.

Bake the bread for 45 minutes to 1 hour. Cover loosely with foil about halfway through to ensure even browning. Poke the center of the bread with a toothpick. If it comes out clean, the bread is done. Oven times will vary between ovens. My bread usually takes 1 hour. Cool bread completely in the pan set on a wire rack.

In a small bowl, whisk the confectioners’ sugar and orange juice together. Add more orange juice depending how thick you want the glaze. Drizzle over cooled bread.

Slice and serve. Cover and store leftover bread at room temperature for 1 day or in the refrigerator for up to 1 week.