Peel the prawns, leaving the tail intact. Make a shallow slit down the back of each prawn and rinse out the dark vein. Pat dry. Cut the crab, widthwise, into 3" long pieces.
Preheat the oven to 450 degrees F.
Place an equal amount of seafood into two individual baking dishes. Combine remaining ingredients, except lemon slices, in a small bowl. Pour over the seafood. Bake 8 to 10 minutes, or just until the seafood is cooked and the crab is heated through. Garnish with lemon slices and serve.