Preheat the oven to 350℉. Butter a medium round or oval casserole dish (2 quart).
In a large bowl, use an electric mixer to combine the butter and sugar. Add the eggs one at a time, beating after each addition. In a separate bowl, whisk together the flour, salt and baking powder. Gradually mix the dry ingredients into the wet ingredients.
Spread the batter into the prepared baking dish. Scatter the raspberries on top. Bake until a toothpick inserted in the center comes out clean, about 45 minutes. Let cool slightly, then serve with whipped cream, ice cream or by itself!