Preheat the oven to 325 degrees F. Butter and flour a 9-inch square cake pan.
Sift the flour and salt into a large bowl. Melt the chocolate with the butter in a double boiler or a bowl set over a pan of hot water (or you can use a microwave). Remove from the heat, add the brown and granulated sugars and leave to dissolve slightly, then stir to combine. Add the eggs, one by one, beating after each addition. The mixture should be very glossy. Gently fold in the flour. Don't overmix.
Spread the batter in the prepared pan to form an even layer. Top with the raspberries and sliced almonds. Bake for 20-30 minutes, or until just set in the middle. A wooden skewer inserted into the center should come out with just a few moist crumbs on it. Don't overbake. Leave to cool in the pan for 30 minutes before cutting into squares and serving.
Recipe courtesy of The Little Red Barn Baking Book (Clarkson Potter, 2000) by Adriana Rabinovich