Preheat the oven to 350 degrees . Lightly grease the bottom and sides of a foil-lined 8-inch square baking pan, then dust with cocoa powder.
In a large saucepan, melt the butter. Remove from the heat and stir in 1 cup sugar, the eggs and vanilla. Stir in 1/2 cup cocoa, the flour and salt until smooth. Spread the brownie batter into the prepared pan and bake until a cake tester or toothpick inserted into the center comes out clean, 25 to 30 minutes. Let cool in the pan. Using a moistened knife, slice into 8 squares, then halve each square on the diagonal to make 16 triangles.
In a medium saucepan, bring the raspberries, remaining 1 tbsp. sugar and 1 tbsp. water to a simmer over medium heat. Cook, mashing the raspberries with a wooden spoon, for 3 minutes. Strain the mixture through a fine-mesh sieve; discard the seeds. Return the sauce to the saucepan and cook over medium heat, stirring, until thick and syrupy, 8 to 10 minutes. Keep warm.
To serve, stand 2 brownie triangles pointy side up in each of 8 bowls. Serve with the ice cream, hot fudge and raspberry sauce.