Place a large pan over medium heat. Add ghee (or butter, oil). Dice the onion and cut the peppers into cubes. Add the vegetables to the pan and sauté for 3 - 4 minutes. Add the diced garlic, ginger, curry paste, curry powder, and tomato paste. Cook for another 2 - 3 minutes.
add the shrimp
Add the coconut milk and water. Bring to a boil, then simmer for 5 minutes for the sauce to thicken. Cut the scallions (spring onions) into 3 cm (1-inch) slices and add to the curry. Add the shrimp and simmer for another 3 - 4 minutes. Season. to taste with salt and pepper. Remove from the heat and stir in the freshly squeezed lime juice.