Place margarine, sugars, and cocoa powder in a bowl and microwave until margarine is melted. Stir until smooth. Next add eggs and vanilla, stir until smooth. Stir in baking powder, salt, and flour.
Add in the blackberries. Gently incorporate. The batter will be very thick. Add sugar to a medium saucepan, and whisk over medium-high heat until all the sugar melts. It will take a minute, but it will melt! Once it becomes a nice reddish-brown color add the butter and stir until melted. Remove from the heat and stir in the half and half.
In a foil lined 8x8 coated with cooking spray press half of the brownie dough into the pan.
Pour the salted caramel over brownie layer.
Top with the other half of the brownie batter.
Bake at 350 for 40-50 minutes, in an 8x8 pan, or until a tester comes out clean.