Preheat oven to 350 degrees. Butter a 2-quart oval or square baking dish. In a large bowl, cream butter and sugar with an electric mixer until fluffy. Add eggs, one at a time, beating after each addition to combine. In a large bowl, whisk together flour, salt, and baking powder; with mixer on low speed, gradually add flour mixture until incorporated.
Spread batter in baking dish. Scatter raspberries on top. Bake until a toothpick inserted in center of cake comes out clean and top is golden brown, 45 to 50 minutes. Let cool 20 minutes; dust with confectioners' sugar, if desired. With a large spoon, scoop out onto serving plates; serve with a dollop of whipped cream, if desired.