Preheat the grill.
In a bowl, mix 1/4 cup olive oil with the Ancho chile powder, garlic, salt and pepper. Add prawns to the oil and refrigerate for at least 2 hours.
To make the salsa, combine the Andy Boy cactus pears and avocado in a mixing bowl, and add onion, cilantro, green onions, olive oil and lemon juice. Season with salt and pepper.
Skewer the prawns on three skewers and grill the prawns for 3 minutes each side. You can serve it over cilantro rice with the salsa on the side.