Cranberry Upside Down Cake

Name: Cranberry Upside Down Cake
Ingredients: 4 tablespoons (55g/2 ounces) unsalted butter (cubed); 3/4 cup (125g) packed light brown sugar; 3 cups (280g/10 ounces) fresh or frozen cranberries; 1 1/4 cups (175g) all-purpose flour; 1/4 cup (50g) coarse cornmeal or polenta; 1 1/2 teaspoons baking powder (preferably aluminum-free); 1/4 teaspoon salt; 1/2 cup (115g/4oz) unsalted butter (cubed, at room temperature); 3/4 cup (150g) granulated sugar; grated zest of one lemon; 2 large eggs (at room temperature); 1 teaspoon vanilla extract; 1/2 cup (125ml) whole or low fat milk (at room temperature)