Prep the pan and oven: Preheat the oven to 350°F (175°C). Grease a 9-inch round cake pan with butter and line the bottom with parchment for an easy release.

Make the cranberry layer: In a medium saucepan, melt 1/2 cup butter over medium heat. Stir in 3/4 cup sugar, orange juice, and zest. Cook 1–2 minutes until glossy and bubbling. Add cranberries and a pinch of salt. Cook 2–3 minutes, stirring, just until some cranberries begin to pop and the mixture thickens slightly. Remove from heat.

Assemble the bottom (which becomes the top): Pour the cranberry mixture into the prepared pan and spread evenly. Tap the pan gently to settle the fruit.

Mix the dry ingredients: In a bowl, whisk flour, baking powder, baking soda, and salt. Set aside.

Mix the wet ingredients: In a larger bowl, whisk melted butter, granulated sugar, and brown sugar until combined. Whisk in eggs one at a time, then add sour cream and vanilla until smooth.

Combine batter: Add the dry ingredients to the wet in two additions, folding gently. If the batter looks very thick, stir in up to 2 tablespoons milk until it’s spreadable but not runny.

Top the cranberries: Dollop the batter over the cranberry layer and spread to the edges with an offset spatula. Work carefully so you don’t disturb the fruit too much.

Bake: Place the pan on a baking sheet to catch any bubble-over. Bake 35–45 minutes, until the top is golden and a toothpick inserted into the cake (not the fruit) comes out clean.

Cool briefly and invert: Let the cake rest 10–15 minutes. Run a knife around the edge. Place a serving plate over the pan and quickly invert. Lift off the pan and peel away parchment. If any berries stick, nudge them back onto the cake.

Serve: Slice warm or at room temperature. Add whipped cream or ice cream for a creamy contrast.