Preheat the oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking pan.

Combine chocolate and butter in a large microwave-safe bowl. Heat in a microwave oven on high power in 30-second increments, stirring between each, until chocolate is completely melted and blended with butter, 2 to 3 minutes.

Add flour, sugar, eggs, vanilla extract, and salt to the bowl with the chocolate and whisk until smooth. Pour into the prepared pan.

Drop dollops of raspberry jam on top and use a knife to swirl into batter. Sprinkle sliced almonds on top.

Bake in the preheated oven until a knife inserted in the center comes out clean, about 25 minutes. Cool completely before slicing, about 30 minutes more.