Preheat oven to 350°F. Line a buttered 8-inch round pan with parchment paper or wax paper, butter the paper, and dust the pan with flour (regular or gluten-free), knocking out the excess.
In the top of a double boiler set over simmering water melt chocolate with jam, stirring, until the mixture is smooth and let it cool.
In the bowl of a stand mixer, beat butter and sugar until the mixture is light and fluffy.
Add eggs, one at a time, beating well after each addition, and mix in chocolate-jam mixture, flour, baking powder, salt, liqueur (or vanilla), and bittersweet chocolate.
Pour batter into prepared pan, smoothing top. Bake cake in middle of the oven for 30 to 40 minutes, or until a cake tester inserted in center comes out with a few crumbs on it.
Let the cake cool in the pan on a rack for 5 minutes, invert it onto the rack, and remove the paper. Let cake torte cool completely.
Before serving, dust with confectioners’ sugar drizzle with Raspberry Sauce (optional).