1-Preparation and Mixing: First, preheat your oven to 350°F and position the rack in the center. This ensures even heat distribution throughout the baking process. Prepare your baking pan by lightly spraying an 8- or 9-inch square baking pan with cooking spray, or alternatively, buttering and flouring it. If you want a more elegant presentation, consider using a 9-inch round springform pan, which also makes serving easier. In a large bowl, combine the ½ cup granulated sugar and 1 teaspoon of freshly grated orange zest. Using your fingers or the back of a spoon, rub the zest into the sugar until it becomes moist and fragrant. This technique helps release the essential oils from the zest, maximizing the orange flavor throughout the cake.

Remember to zest only the outer orange skin and avoid the white pith, which can add an unpleasant bitterness to your cake.

Once the sugar and zest are well combined, whisk in the wet ingredients one by one: ¼ cup melted unsalted butter, ¼ cup orange juice, ¼ cup whole milk, ½ cup sour cream, 1 large egg, and ½ teaspoon vanilla extract. Mix until everything is well incorporated, but be careful not to overmix at this stage.

2-Combining and Baking: Now, add the dry ingredients to the bowl: 1 ¼ cups plus 2 tablespoons of all-purpose flour, ¾ teaspoon baking powder, ¼ teaspoon baking soda, and ¼ teaspoon coarse kosher salt. Whisk everything together for about 10 seconds, just until the batter is mostly smooth. Small lumps are okay overmixing can result in a tough cake. Spread the batter evenly into your prepared pan, using a spatula to smooth the top. Make sure the batter is distributed uniformly to ensure even baking. For the crumb topping, mix ½ cup of all-purpose flour with ⅓ cup granulated sugar, ¼ teaspoon ground cinnamon, ¼ teaspoon ground nutmeg, and ¼ teaspoon coarse kosher salt in a separate bowl. Stir in the ¼ cup melted unsalted butter until the mixture resembles coarse crumbs. If the mixture seems too wet, add an additional ¼ cup of flour to achieve the right texture. Sprinkle this crumb topping evenly over the batter in the pan. Bake for 25-35 minutes, or until a tester inserted in the center comes out clean or with moist crumbs. Baking times may vary depending on your oven and the size of your pan, so start checking at the 25-minute mark.

3-Finishing Touches and Serving: While the cake is cooling slightly on a rack, prepare the icing by whisking together ¾ cup powdered sugar with 1 tablespoon of orange juice until the mixture is smooth and has a drizzly consistency. If it’s too thick, add a tiny bit more orange juice; if too thin, add a little more powdered sugar. Drizzle the icing over the slightly cooled cake, and for an extra touch of flavor and visual appeal, add some freshly grated orange zest or a sprinkle of chopped crystallized ginger on top. Let the cake cool for about 15 minutes before serving warm.