01 - Preheat the oven to 350°F. Grease and line an 8-inch round cake pan with parchment paper.
02 - In a saucepan over medium heat, combine cranberries, sugar, orange juice, water, and orange zest. Cook 5 to 7 minutes, stirring occasionally, until cranberries burst and mixture thickens slightly. Spread evenly in the prepared pan.
03 - In a bowl, whisk together flour, baking powder, and salt.
04 - In a large bowl, cream butter and sugar until light and fluffy. Beat in eggs one at a time, then mix in vanilla extract.
05 - Add dry ingredients to the wet mixture in three parts, alternating with milk. Begin and end with dry ingredients. Mix until just combined without overmixing.
06 - Carefully spoon batter over cranberry topping, smoothing the surface. Bake 35 to 40 minutes, or until a toothpick inserted in the center comes out clean.
07 - Allow cake to cool in the pan for 15 minutes. Run a knife around edges, invert onto a plate, and remove parchment paper.
08 - Serve warm or at room temperature.