Combine butter, brown sugar, Lime Ponzu and lime juice. Remove scales from salmon with a knife, place salmon, skin side down in a baking dish; brush with butter mixture and bake at 375° for 40 minutes, basting with remaining butter mixture. In a blender mix the avocados with sour cream, garlic, olive oil and lemon juice, puree to form the sauce. Serve sliced salmon with a dollop of avocado sauce on top.