tablespoons/85 grams unsalted butter, at room temperature, plus more for greasing the pan
small navel orange (about 250 grams), ends trimmed, cut into large chunks, and seeds removed, if necessary
cup/60 milliliters whole milk
cups/192 grams all-purpose flour
teaspoon baking powder
teaspoon baking soda
teaspoon kosher salt
cup/151 grams granulated sugar
large eggs, at room temperature
- Heat the oven to 350 degrees. Prepare the pan: Butter an 8-inch square baking pan. Line the pan with parchment paper, leaving a 2-inch overhang on two sides. Butter the parchment.
- Transfer the orange chunks and milk to a high-speed blender (or food processor) and process until it is the texture of smooth applesauce. (You should have about 1 generous cup.)
- In a medium bowl, whisk together the flour, baking powder, baking soda and salt.
- In a large bowl with an electric mixer, beat the butter and granulated sugar on medium until light and fluffy, about 3 minutes. Add the eggs, one at a time, scraping down the bowl as needed.
- Add half the flour mixture and beat just until combined. Beat in the orange mixture, then beat in the remaining flour mixture. Transfer the batter to the prepared pan and smooth the top.
- Bake the cake until a toothpick inserted into the center comes out with moist crumbs attached, 35 to 40 minutes. Transfer to a rack to cool for 20 minutes. Then, using the parchment, transfer the cake to a rack to cool completely.
- While the cake cools, prepare the glaze, if using: In a small bowl, whisk together the confectioners’ sugar, orange zest and orange juice. (Use a little less juice for a thicker glaze that will sit on top of the cake, or add a little more juice for a thinner glaze that will soak into the cake.)
- Spread the glaze over the cooled cake, then slice to serve. Store leftovers well-wrapped at room temperature for up to 3 days.